Sarcoidosis

Immune MONDO:0019338 Pathograph 16 Show in embeddings browser Granulomatous Disease Immune-Mediated Disease

Sarcoidosis is a multisystem inflammatory disease of unknown etiology characterized by the formation of non-caseating granulomas, most commonly affecting the lungs and lymph nodes. The leading model holds that genetically susceptible individuals (HLA-DRB1, BTNL2, ANXA11, NOTCH4, IL27RA risk alleles) mount an exaggerated CD4+ T-cell response to a poorly degradable antigen (mycobacterial KatG/ESAT-6, propionibacterial, or environmental dusts), driving Th1/Th17.1-skewed inflammation, IFN-gamma production, and macrophage transformation into epithelioid and multinucleated giant cells organized into granulomas. Macrophage-intrinsic mTORC1 hyperactivation sustains granuloma maintenance and correlates with progressive disease. The disease predominantly affects adults aged 20-40 years, with higher incidence in African Americans and Northern Europeans. Clinical presentation ranges from asymptomatic to severe organ dysfunction; while many cases resolve spontaneously, chronic progressive disease (10-30%) progresses to pulmonary fibrosis, cardiac, neurologic, ocular, or cutaneous involvement.

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Inheritance

Polygenic susceptibility

Sarcoidosis is not a Mendelian disorder but shows familial clustering with polygenic susceptibility (HLA-DRB1, BTNL2, ANXA11). Risk is increased in first-degree relatives.

Show evidence (1 reference)

PMID:27454307 SUPPORT Human Clinical

"Familial clusters can occur."

Familial clustering supports genetic predisposition without Mendelian inheritance.

◆

Subtypes

Pulmonary Sarcoidosis

Most common form, affecting lungs and hilar lymph nodes; staged by chest radiograph findings.

Cardiac Sarcoidosis

Myocardial granulomas causing conduction abnormalities, heart failure, or sudden death.

Neurosarcoidosis

CNS involvement causing cranial neuropathies, meningitis, or mass lesions.

Cutaneous Sarcoidosis

Skin manifestations including erythema nodosum, lupus pernio, and papular lesions.

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Mechanistic Hypotheses

Antigen Persistence / Th17.1 / mTORC1 Granuloma Chronicity Model

antigen_persistence_granuloma_chronicity_model EMERGING Pulmonary Sarcoidosis

Evidence balance 3 partial 1 refute

Sarcoidosis is modeled as a genetically conditioned, antigen-driven granulomatous immune response in which poorly degradable or repeatedly encountered antigens are presented by macrophage-lineage antigen-presenting cells to CD4+ T cells. The activated T-cell compartment polarizes toward IFN-gamma-producing Th17.1/Th1-like effector states while regulatory T-cell restraint is insufficient. This cytokine circuit recruits and activates macrophages, promotes epithelioid and multinucleated giant-cell granuloma architecture, and intersects with macrophage-intrinsic metabolic programs such as mTORC1 activation. Resolution is hypothesized to require antigen clearance or sequestration plus restoration of regulatory and apoptotic checkpoints; chronic disease and fibrosis occur when antigen persistence, Th17.1 feedback, macrophage survival/proliferation, and tissue-repair programs remain engaged.

Retained as EMERGING after the 2026 OpenScientist hypothesis-search report (kb/hypotheses/Sarcoidosis/antigen_persistence_granuloma_chronicity_model/openscientist.md). The report judged the model partially supported: antigen-driven CD4 T-cell responses, Th17.1/Treg imbalance, and macrophage mTORC1 granuloma biology are individually well supported, but the integrated Th17.1-to-macrophage mTORC1 link remains unproven and fibrosis may diverge through distinct profibrotic/EMT-like tissue-remodeling programs. Best current fit is non-Lofgren, chronic/progressive pulmonary sarcoidosis rather than all sarcoidosis phenotypes. The cutaneous CLEAR trial is retained only as cross-organ discordance against the negative pulmonary trial; it does not extend the machine-readable hypothesis scope beyond Pulmonary Sarcoidosis. This model deliberately leaves the antigen source open; the competing vimentin_autoimmunity_model proposes a self-antigen rather than persistent microbial antigen as the disease-defining trigger, and the two are not mutually exclusive because molecular mimicry could unify them.

Pathograph links

Genetic Susceptibility -> Antigen Recognition and CD4+ T-Cell Activation DIRECT Risk alleles in HLA-DRB1 and BTNL2 alter MHC class II antigen presentation and T-cell co-inhibition, lowering the threshold for an exaggerated CD4+ T-cell response to a triggering antigen.

Antigen Recognition and CD4+ T-Cell Activation -> Th17.1 Polarization and IFN-gamma Production DIRECT Antigen-activated CD4+ T cells in lung tissue polarize toward an IFN-gamma-producing Th17.1 phenotype that drives sustained granulomatous inflammation.

Th17.1 Polarization and IFN-gamma Production -> Macrophage Activation and mTORC1 Hyperactivation INDIRECT UNKNOWN INTERMEDIATES IFN-gamma-rich Th17.1 inflammation, persistent antigen, and other tissue signals are hypothesized to converge on recruitment, activation, and metabolic reprogramming of macrophages; direct Th17.1-to-macrophage mTORC1 causality in human sarcoidosis remains unproven. Intermediates: Unresolved coupling between Th17.1 cytokines, persistent antigen, macrophage growth/survival signals, and macrophage mTORC1 activation.

Macrophage Activation and mTORC1 Hyperactivation -> Granuloma Formation DIRECT mTORC1-driven hypertrophic, proliferating macrophages aggregate with multinucleated giant cells and CD4+ T cells to form non-caseating granulomas.

Granuloma Formation -> Fibrotic Tissue Remodeling INDIRECT UNKNOWN INTERMEDIATES Persistent granulomatous inflammation is associated with later TGF-beta-driven myofibroblast programs and excessive ECM deposition in a subset of patients, but the switch from active granulomas to fibrotic remodeling is not resolved and may involve partly distinct profibrotic pathways. Intermediates: Unresolved granuloma-to-fibrosis switch involving TGF-beta signaling, epithelial-mesenchymal transition-like programs, fibroblast activation, and chronic tissue injury.

Deep research

OpenScientist citations 22 citations 2026-07-26T03:11:42.451542

Show evidence (4 references)

PMID:38165044 PARTIAL Other

"Sarcoidosis is a complex immune-mediated disease characterized by clusters of immune cells called granulomas."

Recent mechanistic review used as the seed reference for the hypothesis-search deep-research run and for the antigen/T-cell/macrophage granuloma-chronicity framing.

PMID:31273209 PARTIAL Other

"The disease develops in genetically predisposed individuals with exposure to an as-yet unknown antigen."

Nature Reviews Disease Primers review supports the central upstream premise of this hypothesis: genetically predisposed patients encounter an unknown antigenic trigger.

PMID:23863960 PARTIAL Human Clinical

"For the primary end point of change in lesion size, as evidenced by a reduction in lesion diameter and number of granulomas, 7 of 10 patients randomized to the CLEAR regimen met this benchmark compared with 0 of 7 randomized to placebo (P = .01, Fisher exact test)."

This small cutaneous-sarcoidosis trial supplies organ-specific clinical support for an antimicrobial-responsive process, but antibiotic immunomodulation, the small analyzed sample, and lack of organism identification prevent inference that viable mycobacteria maintain pulmonary granulomas.

+ 1 more reference

Vimentin Autoantigen / HLA-DRB1*03 Autoimmunity Model

vimentin_autoimmunity_model EMERGING Pulmonary Sarcoidosis

Evidence balance 5 support 3 partial

An alternative to the persistent-microbial-antigen premise: in a subset of patients - most clearly the HLA-DRB1*03+ Lofgren phenotype - the disease-defining antigen is a self-protein rather than a foreign one, with the cytoskeletal protein vimentin as the leading candidate autoantigen. HLA-DRB1*03 presents vimentin-derived peptides to a strikingly restricted CD4+ T-cell receptor repertoire (Valpha2.3/Vbeta22), and linked T- and B-cell autoreactivity to vimentin is demonstrable in situ in the sarcoid lung. Under this model sarcoidosis (or at least its resolving HLA-restricted form) is better understood as an antigen-specific autoimmune disease. Rather than a strict self-versus-foreign dichotomy, the best-supported reading (2026 OpenScientist hypothesis-search report) is a multi-antigen milieu in the DR3+ sarcoid lung: HLA-DR molecules present several self-peptides, but only the vimentin response is demonstrably HLA-DRB1*03-restricted, whereas T-cell responses to ATP synthase and lysyl-tRNA synthetase also occur in DR3-negative patients, and the microbial antigen mycobacterial catalase-peroxidase (mKatG) is an independently documented tissue antigen whose relationship to the Valpha2.3/Vbeta22 repertoire has not been directly tested. Vimentin is thus one prominent antigen among several rather than the unique disease initiator. The downstream CD4+ T-cell activation and Th17.1 effector chain is shared with the antigen-persistence model, and a direct molecular-mimicry bridge between vimentin and mycobacterial proteins remains speculative and is not supported at the linear-sequence level.

Held at EMERGING: the vimentin-autoantigen and HLA-DRB1*03/Valpha2.3-Vbeta22 associations are well documented for pulmonary/Lofgren sarcoidosis, but vimentin is not proven to be the (or a) universal disease-initiating antigen, and the model is best supported in HLA-DRB1*03+ patients rather than across all sarcoidosis. Two caveats from the OpenScientist hypothesis-search report (kb/hypotheses/Sarcoidosis/vimentin_autoimmunity_model/openscientist.md; assessment sidecar under that directory's assessments/): (1) anti-vimentin autoreactivity is not sarcoidosis-specific (also in lupus nephritis and, as anti-citrullinated vimentin, rheumatoid arthritis), weakening its role as a disease-defining antigen; and (2) the resolution paradox - HLA-DRB1*03, the allele anchoring the model, is a dominant good-prognosis allele predicting spontaneous resolution, better fitting antigen recognition coupled to effective clearance than a self-perpetuating chronic autoimmune attack.

Pathograph links

Genetic Susceptibility -> Self-Antigen Vimentin Presentation by HLA-DRB1*03 DIRECT In the vimentin autoimmunity model specifically, the HLA-DRB1*03 risk allele presents the self-peptide vimentin (Vim)429-443 to the restricted Valpha2.3/Vbeta22 CD4+ T-cell repertoire - the model-distinguishing self-antigen presentation step.

Self-Antigen Vimentin Presentation by HLA-DRB1*03 -> Antigen Recognition and CD4+ T-Cell Activation DIRECT HLA-DRB1*03-presented vimentin peptide is recognized by the restricted Valpha2.3/Vbeta22 CD4+ T cells, feeding the shared antigen-recognition and Th17.1 effector chain.

Deep research

OpenScientist citations 9 citations 2026-07-31T16:53:24.856197

Show evidence (8 references)

PMID:30038611 SUPPORT Human Clinical

"Vimentin has been implicated in pulmonary sarcoidosis as a T-cell autoantigen"

Directly establishes vimentin as an implicated T-cell autoantigen in pulmonary sarcoidosis in the HLA-DRB1*03 / restricted-TCR / Lofgren context, the central premise of this alternative hypothesis.

PMID:30038611 SUPPORT Human Clinical

"linked in situ recognition of vimentin by both T- and B-cells in HLA-DRB1*03+ sarcoidosis patients"

Demonstrates coordinated T- and B-cell autoreactivity to vimentin within the HLA-DRB1*03+ sarcoid lung, supporting an antigen-specific autoimmune mechanism rather than a purely foreign-antigen response.

PMID:26585430 SUPPORT Human Clinical

"Simultaneous expression of Vα2.3 with the Vβ22 chain was identified in the lungs of all HLA-DRB1*03(+) patients."

Directly documents the restricted Vα2.3/Vβ22 CD4+ T-cell receptor repertoire in HLA-DRB1*03-positive pulmonary sarcoidosis.

+ 5 more references

Environmental Exposure × Host Susceptibility Trigger Model

environmental_exposure_host_susceptibility_trigger_model EMERGING Pulmonary Sarcoidosis

Evidence balance 5 partial

Specific inhaled bioaerosols and inorganic particles are associated with pulmonary-sarcoidosis risk. The hypothesis is that, in a subset of susceptible hosts, a particular exposure initiates disease through an exposure-specific innate-sensing or antigen-presentation program that changes CD4+ T-cell polarization. HLA and other immune-risk alleles may modify that response and the resulting phenotype. This upstream model complements the antigen-persistence/granuloma-chronicity model; it does not assert that distinct exposure classes share one receptor or pathway. The exposure-to-sensor/presentation bridge and exposure-by-genotype combinations remain unproven.

Retained as EMERGING after the 2026 disease-level and focused OpenScientist reports (research/Sarcoidosis-deep-research-openscientist.md and kb/hypotheses/Sarcoidosis/environmental_exposure_host_susceptibility_trigger_model/openscientist.md). Human data support modest exposure associations and host-genetic main effects. Direct ACCESS HLA-by-exposure signals remain exploratory and unreplicated; separate single-cohort genome-wide analyses report smoking-by-locus and insecticide-by-locus interactions, but do not replicate the ACCESS pairs. A WTC study found no interaction with its exposure-degree measure, and no exposure-specific sensor-to-CD4 mechanism has been shown in idiopathic sarcoidosis. Beryllium-associated granulomatous disease is a separate exposure-defined differential diagnosis, not evidence that its HLA-restricted mechanism operates in idiopathic pulmonary sarcoidosis. No exposure-specific causal edge is curated.

Deep research

OpenScientist citations 2026-07-26T03:30:55.985074

Show evidence (5 references)

PMID:15347561 PARTIAL Human Clinical

"In multivariable modeling, we observed elevated ORs for work in areas with musty odors (OR 1.62, CI 1.24-2.11) and with occupational exposure to insecticides (OR 1.61, CI 1.13-2.28), and a decreased OR related to ever smoking cigarettes (OR 0.65, CI 0.51-0.82)."

The matched ACCESS case-control study supports modest, exposure-class associations, not a specific initiating antigen, receptor, or causal pathway; questionnaire exposure ascertainment and residual confounding remain limitations.

PMID:19382531 PARTIAL Human Clinical

"Significant interaction was observed between HLA DRB1*1101 and insecticide exposure at work (p < 0.10) and suggestive interaction was observed between HLA DRB1*1101 and exposure to mold and musty odors and DRB1*1501 and insecticide exposure at work (P < 0.15)."

The ACCESS case-control analysis provides exposure-by-HLA leads, but its exploratory significance thresholds and phenotype stratification require independent replication before these pairs are modeled as causal.

PMID:31819081 PARTIAL Human Clinical

"Assessment of smoking effects with inclusion of genetic information revealed 53 (in LS) and 34 (in non-LS) SNP-smoking additive interactions at false discovery rate (FDR) below 5%. The lead signals interacting with smoking were rs12132140 (AP = 0.56, 95% CI = 0.22-0.90), p = 1.28e-03) in FCRL1..."

This Swedish case-control study supports subgroup-specific, genotype-dependent smoking interactions in one cohort. It does not replicate the ACCESS HLA-exposure pairs, identify an initiating antigen or sensor, or establish a causal smoking effect; independent and functional replication remain necessary.

+ 2 more references

Discussions and Knowledge Gaps

Which antigenic triggers and host immune-cell circuits determine whether a sarcoidosis granuloma resolves, persists as chronic inflammatory disease, or transitions to fibrotic organ damage?

KNOWLEDGE GAP OPEN gap_sarcoidosis_antigen_persistence_resolution

Attached to

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation pathophysiology#Th17.1 Polarization and IFN-gamma Production pathophysiology#Macrophage Activation and mTORC1 Hyperactivation pathophysiology#Granuloma Formation pathophysiology#Fibrotic Tissue Remodeling

The entry captures a plausible antigen-driven CD4 T-cell, Th17.1, Treg, macrophage, and mTORC1 cascade, but the disease-defining upstream antigen remains unknown and the switch from spontaneous resolution to chronic granuloma persistence or fibrosis is not causally resolved. This matters because current treatment suppresses granulomatous inflammation after organ dysfunction appears; it does not yet stratify patients by antigen source, antigen clearance, granuloma metabolic state, or fibrotic transition risk.

Proposed experiments

Longitudinal sarcoidosis granuloma antigen and resolution map

longitudinal human granuloma perturbation experiment

exp_sarcoidosis_longitudinal_granuloma_resolution_map

Profile newly diagnosed sarcoidosis patients with paired bronchoalveolar lavage, blood, and when clinically obtained granuloma biopsies at diagnosis and follow-up. Combine antigen discovery (mycobacterial/propionibacterial/environmental peptide and nucleic-acid panels), TCR clonotype tracking, spatial single-cell transcriptomics, and perturbation of patient-derived macrophage/T-cell cultures with antigen withdrawal, Treg-restoring conditions, IFN-gamma/JAK blockade, and mTORC1 inhibition. Compare patients who spontaneously remit with those who develop chronic pulmonary disease or fibrosis.

Model systems

Patient-derived pulmonary sarcoidosis immune-cell culture

Paired bronchoalveolar lavage and biopsy-derived macrophage-lineage cells, CD4+ T cells, and fibroblast-containing granuloma explant or coculture systems from remitting and chronic/progressive sarcoidosis patients.

PRIMARY CELL CULTURE

human NCBITaxon:9606

lung UBERON:0002048

alveolar macrophage CL:0000583 CD4-positive helper T cell CL:0000492 fibroblast CL:0000057

Perturbations

Antigen candidate exposure and withdrawal

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation

Test whether candidate microbial, self, or environmental antigens maintain TCR clonotype activation and granuloma-like organization, and whether withdrawal collapses the inflammatory program.

Effect: antigen presence versus clearance

mTORC1 and IFN-gamma/JAK pathway blockade

pathophysiology#Macrophage Activation and mTORC1 Hyperactivation

Compare rapamycin/everolimus-like mTORC1 inhibition and JAK blockade for their ability to induce macrophage apoptosis, reduce glycolytic granuloma-state markers, and interrupt Th17.1-macrophage feedback.

Effect: decreased granuloma persistence signaling

Readouts

Antigen-specific TCR clonotype persistence

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation

Persistence or contraction of antigen-reactive CD4+ T-cell clonotypes over time and after antigen withdrawal in culture.

Progressive macrophage metabolic state

pathophysiology#Macrophage Activation and mTORC1 Hyperactivation

p-S6, Ki-67, glycolysis, and apoptosis readouts that distinguish remitting from chronic/progressive granuloma macrophages.

Fibrotic transition signal

pathophysiology#Fibrotic Tissue Remodeling

Spatial TGF-beta signaling, fibroblast activation, extracellular matrix organization, and pulmonary-function trajectory used to determine whether persistent granuloma circuits predict fibrotic organ damage.

Decision criterion

The antigen-persistence model would be strengthened if remitting patients show antigen-reactive clonotype contraction and loss of macrophage mTORC1/glycolytic signals, while chronic or fibrotic patients retain antigen-reactive clonotypes, Th17.1/Treg imbalance, macrophage p-S6/Ki-67 activity, and fibroblast activation despite standard immunosuppression.

Show evidence (3 references)

PMID:31273209 SUPPORT Other

"The disease develops in genetically predisposed individuals with exposure to an as-yet unknown antigen."

Establishes unknown antigen identity as a central unresolved upstream causal step.

PMID:33329511 SUPPORT Other

"Over half of patients with sarcoidosis will incur spontaneous resolution or never have clinical manifestations of the disease, whereas the remaining half will experience a more chronic course, often requiring treatment."

Supports the resolution-versus-chronicity split that the proposed longitudinal experiment is designed to distinguish.

PMID:38165044 SUPPORT Other

"Despite major steps in understanding the cause of this disease, many questions remain."

Recent mechanistic review explicitly frames granuloma-cause and granuloma-mechanism uncertainty as an active knowledge gap.

Which inhaled exposure classes, host genotypes, innate sensors, and HLA-restricted antigens form a reproducible causal chain from exposure to CD4+ T-cell polarization and pulmonary granuloma initiation in idiopathic sarcoidosis?

KNOWLEDGE GAP OPEN gap_sarcoidosis_exposure_genotype_trigger_mechanism

Attached to

environmental#Occupational Exposures pathophysiology#Genetic Susceptibility pathophysiology#Antigen Recognition and CD4+ T-Cell Activation pathophysiology#Th17.1 Polarization and IFN-gamma Production pathophysiology#Granuloma Formation

Case-control studies associate several bioaerosol and inorganic-particle exposures with sarcoidosis, and host genetic susceptibility is well established, but association does not identify an initiating antigen or receptor. The published ACCESS HLA-by-exposure leads use exploratory thresholds and lack independent replication. Separate single-cohort genome-wide analyses report smoking interactions at FCRL1 and IL23R and suggestive insecticide interactions at two loci, but neither independently replicates the ACCESS pairs or supplies the missing mechanism; a WTC cohort did not detect interaction with its exposure-degree measure. No non-beryllium exposure has been linked in idiopathic sarcoidosis through a defined sensor, HLA-presented antigen, antigen-specific CD4 response, and granuloma phenotype. Exposure-defined mimics such as chronic beryllium disease must be excluded rather than generalized to idiopathic disease. The required epidemiologic interaction and cellular causal chain should therefore be tested separately and then connected only if both replicate.

Proposed experiments

Preregistered exposure-by-HLA replication in incident pulmonary sarcoidosis

prospective exposure-genotype interaction study

exp_sarcoidosis_exposure_hla_interaction_replication

Enroll treatment-naive incident pulmonary-sarcoidosis cases and matched controls in two independent, ancestry-diverse cohorts. Ascertain prespecified mold/microbial-bioaerosol, insecticide, silica/inorganic-dust, and WTC-like mixed-particle exposures with blinded industrial-hygiene review, job-exposure matrices, and quantitative duration or dose rather than case-only recall. Exclude or separately adjudicate chronic beryllium disease with exposure history and beryllium lymphocyte proliferation testing when appropriate, as well as silicosis and hypersensitivity pneumonitis. Genotype HLA class II and established risk loci. Estimate exposure main effects and additive and multiplicative genotype-by-exposure interactions with ancestry, smoking, occupation, geography, and socioeconomic confounders prespecified; replicate each exposure-allele pair and phenotype stratum before mechanistic follow-up.

Readouts

Exposure-class association

environmental#Occupational Exposures

Exposure-specific adjusted effect estimates with dose-response, temporality, negative-control exposures, and between-cohort replication.

Direction: THRESHOLD DEPENDENT

Interpretation: A modest main effect can prioritize an exposure class but cannot alone establish a trigger mechanism.

Replicated genotype-by-exposure interaction

pathophysiology#Genetic Susceptibility

Prespecified additive and multiplicative interaction estimates for each HLA or non-HLA risk allele and exposure class, including confidence intervals and independent-cohort replication.

Direction: THRESHOLD DEPENDENT

Interpretation: Only a replicated interaction with exposure preceding disease prioritizes a specific host-exposure pair for the cellular experiment.

Incident granulomatous disease phenotype

pathophysiology#Granuloma Formation

Centrally adjudicated incident pulmonary sarcoidosis, organ pattern, and Löfgren versus non-Löfgren presentation and acute-resolving versus chronic or fibrotic course.

Direction: POSITIVE

Controls

Exposed unaffected controls

Participants with comparable measured exposure and ancestry who do not develop sarcoidosis, separating exposure from disease response.

Genetically matched unexposed controls

Participants carrying the candidate allele without the candidate exposure, separating genotype from the interaction.

Negative-control exposure and allele pairs

Prespecified unrelated exposures and alleles used to detect recall, occupational, ancestry, or multiple-testing artifacts.

Decision criterion

The gene-environment arm is supported only when the same prespecified exposure-allele pair shows exposure-before-disease temporality, a corrected interaction effect beyond both main effects, a compatible dose-response, and directionally consistent replication. Main effects without interaction support only separate exposure and host-risk nodes. A well-powered null interaction across both cohorts would weaken that specific pair, not exclude other exposures, alleles, or non-genetic susceptibility.

Would support

mechanistic_hypothesis#environmental_exposure_host_susceptibility_trigger_model

Exposure-matched sensor-to-HLA-to-CD4 pulmonary causal-chain assay

exposure-stratified pulmonary immune-cell perturbation assay

exp_sarcoidosis_exposure_sensor_hla_causal_chain

For exposure-allele pairs that replicate epidemiologically, compare bronchoalveolar antigen-presenting cells and autologous CD4+ T cells from treatment-naive pulmonary-sarcoidosis cases, exposed unaffected controls, and allele-matched unexposed controls. Apply chemically and microbiologically characterized matched and mismatched exposure preparations in a short time course. Use orthogonal blockade or editing of response-nominated innate sensors and HLA class II, then measure early antigen-presenting-cell responses, HLA-bound peptides, antigen-specific TCR activation, Th1/Th17.1 polarization, and granuloma-like organization. Advance only exposure preparations that are endotoxin-controlled, noncytotoxic, and reproducible across donors.

Model systems

Autologous alveolar antigen-presenting-cell and CD4+ T-cell coculture

Bronchoalveolar macrophage or dendritic-cell preparations cocultured with autologous CD4+ T cells from cases and matched control groups.

CO CULTURE

human NCBITaxon:9606

lung UBERON:0002048

alveolar macrophage CL:0000583 conventional dendritic cell CL:0000990 CD4-positive helper T cell CL:0000492

Perturbations

Matched and mismatched exposure challenge

environmental#Occupational Exposures

Compare the epidemiologically matched exposure preparation with other exposure classes, vehicle, and dose-matched particle or bioaerosol controls.

Effect: exposure-class-specific challenge

Candidate innate-sensor loss or blockade

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation

Perturb only sensors nominated by an early reproducible response, using genetic and pharmacologic approaches with on-target rescue where feasible.

Effect: reduced candidate exposure sensing

HLA class II blockade

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation

Block the implicated HLA-DR or HLA-DP presentation step and compare it with isotype and irrelevant-HLA controls.

Effect: reduced HLA-restricted antigen presentation

Readouts

Early antigen-presenting-cell response

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation

Time-resolved uptake, viability, sensor-proximal signaling, cytokines, costimulatory state, and HLA class II surface abundance before T-cell activation.

Direction: POSITIVE

Exposure-linked HLA immunopeptidome and TCR response

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation

Exposure-derived or exposure-modified-self HLA-bound peptides, peptide-specific tetramer responses, and activation of expanded granuloma-linked TCR clonotypes.

Direction: POSITIVE

CD4+ T-cell polarization

pathophysiology#Th17.1 Polarization and IFN-gamma Production

Antigen-specific IFN-gamma/IL-17A production, Th1/Th17.1 state, and Treg balance after matched versus mismatched challenge.

Direction: POSITIVE

Granuloma-like organization

pathophysiology#Granuloma Formation

Multicellular aggregate formation, macrophage epithelioid state, and spatial T-cell/macrophage organization distinguished from nonspecific toxicity or foreign-body aggregation.

Direction: POSITIVE

Controls

Exposed unaffected donor cells

Tests whether the candidate response is a generic consequence of exposure rather than a disease- or susceptibility-linked response.

Allele-matched unexposed donor cells

Separates the candidate HLA background from prior exposure.

Endotoxin, viability, and generic-particle controls

Exclude contaminant-driven innate activation, cytotoxicity, and nonspecific foreign-body aggregation.

Matched versus mismatched exposure and HLA controls

Test the exposure and restriction-element specificity required by the hypothesis rather than generic immune hyperreactivity.

Granulomatous disease controls

Include exposure-defined chronic beryllium disease, silicosis, and hypersensitivity pneumonitis samples where available to distinguish an idiopathic-sarcoidosis response from known exposure diseases or generic granulomatous inflammation.

Decision criterion

A specific trigger chain is supported only if a replicated exposure-allele pair produces an early, noncytotoxic exposure-class-specific antigen-presenting-cell response; yields a defined HLA-bound antigen or modified-self peptide and cognate TCR activation; precedes CD4 polarization and granuloma-like organization; and loses those downstream readouts after orthogonal sensor and restriction-element perturbation. Generic inflammation, aggregation without antigen-specific T-cell activation, a response shared by exposed unaffected controls, or microbial-antigen responses independent of the recorded exposure would favor toxicity, foreign-body, or antigen-persistence alternatives. Failure after adequate target engagement weakens only the tested exposure-sensor-HLA chain.

Would support

mechanistic_hypothesis#environmental_exposure_host_susceptibility_trigger_model

Show evidence (1 reference)

PMID:30134122 PARTIAL In Vitro

"Compared with identically treated PBMCs of control subjects (n = 5), purified protein derivative-treated sarcoidosis PBMCs (n = 6) were distinguished by the formation of cellular aggregates resembling granulomas."

This small patient-cell study provides feasibility precedent for case-control antigen challenge and granuloma-like readouts, not evidence for a particular environmental exposure in vivo.

Show evidence (6 references)

PMID:42471775 SUPPORT Other

"Several environmental exposures are associated with a risk for sarcoidosis, but their exact role is incompletely understood."

The source review states the unresolved causal role that defines this knowledge gap.

PMID:15347561 PARTIAL Human Clinical

"The study did not identify a single, predominant cause of sarcoidosis. We identified several exposures associated with sarcoidosis risk, including insecticides, agricultural employment, and microbial bioaerosols."

The primary ACCESS study supplies exposure-class associations while explicitly failing to identify one cause or a mechanistic chain.

PMID:19382531 PARTIAL Human Clinical

These exploratory interaction thresholds motivate preregistered replication but are insufficient for a causal exposure-allele edge.

+ 3 more references

Why does sarcoidosis combine vigorous compartmentalized granulomatous CD4+ Th1/Th17.1 activity at disease sites with peripheral T-cell lymphopenia, anergy, and PD-1+ exhaustion, and would restoring exhausted T-cell function promote resolution or instead intensify granulomatous inflammation?

KNOWLEDGE GAP OPEN gap_sarcoidosis_immunologic_paradox_anergy_vs_activation

Attached to

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation pathophysiology#Th17.1 Polarization and IFN-gamma Production

Sarcoidosis presents a long-standing immunologic paradox: an exaggerated, IFN-gamma-rich local granulomatous CD4+ T-cell response coexists with systemic hyporesponsiveness - cutaneous anergy, peripheral CD4+ lymphopenia, reduced proliferation on TCR stimulation, and PD-1+ exhaustion markers. This matters therapeutically and is directionally unresolved: CD4+ T-cell exhaustion reverses in patients who spontaneously remit (suggesting exhaustion tracks with, and may even favor, resolution), yet checkpoint-inhibitor cancer therapy that reverses T-cell exhaustion can precipitate sarcoid-like granulomatous reactions. Whether checkpoint restoration would clear persistent antigen and resolve disease or instead reignite granuloma formation is unknown, and the entry's antigen/T-cell nodes do not currently capture this exhaustion axis.

Proposed experiments

Longitudinal T-cell exhaustion versus resolution tracking with ex vivo checkpoint modulation

longitudinal immunophenotyping with ex vivo checkpoint perturbation

exp_sarcoidosis_tcell_exhaustion_resolution_tracking

In newly diagnosed sarcoidosis patients, serially phenotype paired peripheral-blood and bronchoalveolar-lavage CD4+ T cells for exhaustion (PD-1, TIM-3, LAG-3), proliferative capacity, Th1/Th17.1 cytokine output, and apoptosis, stratifying by subsequent spontaneous resolution versus chronic/progressive course. In parallel, apply ex vivo PD-1/PD-L1 blockade to patient-derived cells and PBMC granuloma-in-a-dish models to test whether reversing exhaustion enhances antigen clearance or amplifies granuloma formation.

Model systems

Paired blood and BAL CD4+ T cells with PBMC granuloma model

Serial peripheral-blood and bronchoalveolar-lavage CD4+ T cells from remitting and chronic sarcoidosis patients, plus autologous PBMC-derived granuloma-in-a-dish cultures for checkpoint-modulation readouts.

PRIMARY CELL CULTURE

human NCBITaxon:9606

lung UBERON:0002048

CD4-positive helper T cell CL:0000492

Readouts

T-cell exhaustion trajectory versus clinical course

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation

PD-1/TIM-3/LAG-3 expression, proliferative capacity, and apoptosis over time, compared between patients who spontaneously resolve and those who progress.

Effect of checkpoint blockade on granuloma output

pathophysiology#Th17.1 Polarization and IFN-gamma Production

Change in Th17.1/IFN-gamma output and granuloma-like aggregate formation after ex vivo PD-1/PD-L1 blockade, to determine whether exhaustion reversal favors resolution or amplifies granulomatous inflammation.

Decision criterion

The exhaustion axis would be clarified if spontaneous resolvers show reversal of the exhaustion phenotype with restored antigen clearance, while ex vivo checkpoint blockade in chronic-disease cells amplifies Th17.1/IFN-gamma output and granuloma formation - indicating exhaustion is a brake whose removal is pathogenic rather than therapeutic in established disease.

Show evidence (2 references)

PMID:29234685 SUPPORT Human Clinical

"sarcoidosis CD4+ T cells demonstrated reductions in Th1 cytokine expression, proliferative capacity (p < 0.05), enhanced apoptosis (p < 0.01), and increased PD-1 expression (p < 0.001)."

Quantifies the peripheral/systemic arm of the paradox - reduced proliferation, cytokine output, and increased PD-1 exhaustion markers on sarcoidosis CD4+ T cells despite active granulomatous disease.

PMID:29234685 SUPPORT Human Clinical

"Reversal of CD4+ T cell exhaustion was observed in subjects undergoing spontaneous resolution"

Directly links reversal of the exhaustion phenotype to spontaneous clinical resolution, framing the central unresolved directional question of whether exhaustion is protective or pathogenic.

Is the disease-defining sarcoidosis antigen self (vimentin) or foreign (mycobacterial mKatG), or is there no true dichotomy because one HLA-DRB1*03-restricted public TCR recognizes several antigens - and why does HLA-DRB1*03, the allele anchoring the antigen-specific response, predict spontaneous resolution rather than chronic disease?

KNOWLEDGE GAP OPEN gap_sarcoidosis_dr3_antigen_identity_and_resolution_paradox

Attached to

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation

A 2026 OpenScientist hypothesis-search of the vimentin_autoimmunity_model surfaced two coupled unknowns. First, the antigen identity is unresolved and the self-versus-foreign framing may be false: the DR3+ sarcoid lung presents a milieu of antigens, but only the vimentin T-cell response is demonstrably HLA-DRB1*03-restricted, whereas responses to ATP synthase and lysyl-tRNA synthetase also occur in DR3-negative patients and the microbial antigen mKatG is documented as a tissue antigen whose relationship to the Valpha2.3/Vbeta22 repertoire has not been directly tested. Whether these antigens converge on the same public clone is unknown, and the molecular-mimicry bridge that would unify self and foreign is unsupported at the linear-sequence level. Second, and paradoxically, HLA-DRB1*03 - the allele that anchors this antigen-specific response - is a dominant good-prognosis allele predicting spontaneous resolution, which is hard to reconcile with classic self-perpetuating autoimmunity and instead favors an antigen-recognition-coupled-to-effective-clearance model. Resolving the antigen identity and the resolution paradox would determine whether the DR3-restricted response is a driver to be suppressed or a clearance program to be supported.

Proposed experiments

HLA-DR3 tetramer multi-antigen ranking against clinical course

HLA class II tetramer antigen-ranking study

exp_sarcoidosis_dr3_tetramer_antigen_ranking

In HLA-DRB1*03+ patients stratified by Lofgren/resolving versus non-resolving course (and DR3+ healthy controls), quantify the frequency and avidity of CD4+ T cells binding HLA-DR3 tetramers loaded in parallel with vimentin (Vim429-443), ATP synthase, lysyl-tRNA synthetase, and mKatG peptides, using paired bronchoalveolar-lavage and blood samples, and relate antigen-specific frequencies to spontaneous resolution versus progression.

Model systems

HLA-DRB1*03+ sarcoidosis BAL and blood CD4+ T cells

Paired bronchoalveolar-lavage and peripheral-blood CD4+ T cells from HLA-DRB1*03+ resolving and non-resolving sarcoidosis patients and DR3+ controls, interrogated with a panel of DR3 peptide tetramers.

PRIMARY CELL CULTURE

human NCBITaxon:9606

lung UBERON:0002048

CD4-positive helper T cell CL:0000492

Readouts

Antigen-specific tetramer frequency versus disease course

pathophysiology#Antigen Recognition and CD4+ T-Cell Activation

Relative frequency and avidity of vimentin-, ATP-synthase-, lysyl-tRNA-synthetase-, and mKatG-tetramer+ CD4+ T cells, compared between resolving and non-resolving DR3+ patients, testing whether any single antigen dominates and whether antigen-reactivity tracks with resolution.

Decision criterion

The single-antigen vimentin model would be supported if vimentin-tetramer+ cells dominate and predict outcome; the shared multi-antigen program would be supported if several antigens engage the restricted TCR at comparable frequency; and the clearance reframing would be supported if higher antigen-specific frequencies track with spontaneous resolution rather than progression.

Show evidence (3 references)

PMID:19786367 SUPPORT Human Clinical

"BAL T cell responses against peptides derived from ATP synthase or from lysyl-tRNA synthetase were detected in DRB10301(pos) as well as DRB10301(neg) patients"

Documents multiple HLA-DR-presented antigens beyond vimentin, motivating the shared multi-antigen framing over a single disease-defining antigen.

PMID:15753209 SUPPORT Human Clinical

"suggesting that remnant mycobacterial catalase-peroxidase is one target of the adaptive immune response driving granulomatous inflammation in sarcoidosis"

Establishes a microbial antigen (mKatG) as a competing target of the same adaptive response, the foreign-antigen pole of the unresolved antigen-identity question.

PMID:20187937 SUPPORT Human Clinical

"DRB1*07, DRB1*14 and DRB1*15 generally associated with, while DRB1*01 and DRB1*03 protected against, a non-resolving disease"

Quantifies the resolution paradox: DR3 protects against non-resolving disease, the observation the proposed experiment is designed to reconcile with an antigen-specific mechanism.

Does the vimentin-immunization-plus-vimentin-bead mouse granuloma model reflect the mechanism of spontaneous human sarcoidosis, or does forced immunization and particulate bead challenge bypass the (unknown) natural initiating events - i.e., is vimentin a genuine initiating autoantigen in humans or only sufficient to drive granulomas once immunity is artificially established?

HUMAN MODEL MISMATCH OPEN gap_sarcoidosis_vimentin_mouse_model_translational_validity

Attached to

pathophysiology#Self-Antigen Vimentin Presentation by HLA-DRB1*03 pathophysiology#Granuloma Formation

PMID:35434591 is the only causal (rather than associative) support for the vimentin autoimmunity model: vimentin-immunized mice challenged with vimentin-coated beads develop sarcoid-like Th1/Th17 lung granulomas. This is genuine mechanistic evidence that anti-vimentin immunity is sufficient to produce sarcoid-like pathology, but its translational validity is uncertain - the model requires deliberate immunization against vimentin plus an intravenous particulate (bead) challenge, neither of which is a documented step in spontaneous human disease, and the model also engaged ILC2/TH2 programs not central to human sarcoid granulomas. Per the KB convention this is a HUMAN_MODEL_MISMATCH (model evidence exists; human translational validity is the open question), not a generic knowledge gap: the question is not whether vimentin autoimmunity can cause granulomas but whether it initiates them in humans.

Proposed experiments

Test for spontaneous anti-vimentin priming preceding human sarcoidosis

pre-symptomatic cohort plus spontaneous-model translational test

exp_sarcoidosis_vimentin_natural_initiation_test

In pre-symptomatic or incident human cohorts (e.g. HLA-DRB1*03+ individuals, or biobank samples predating diagnosis), determine whether anti-vimentin T-/B-cell responses and Valpha2.3/Vbeta22 clonal expansion arise before clinical granulomatous disease and without an obvious immunizing event, and whether they track antigen exposure. In parallel, develop a spontaneous (non-immunization, non-bead) model or ex vivo human granuloma-in-a-dish system to test whether endogenously processed vimentin is sufficient to nucleate granuloma formation.

Model systems

Pre-diagnosis human cohort and non-immunization granuloma model

Incident/pre-symptomatic HLA-DRB1*03+ human samples paired with a spontaneous or ex vivo human granuloma model that does not rely on forced vimentin immunization or particulate bead challenge.

PRIMARY CELL CULTURE

human NCBITaxon:9606

lung UBERON:0002048

CD4-positive helper T cell CL:0000492

Readouts

Temporal order of anti-vimentin immunity versus disease onset

pathophysiology#Self-Antigen Vimentin Presentation by HLA-DRB1*03

Whether anti-vimentin T-/B-cell reactivity and Valpha2.3/Vbeta22 clonal expansion precede clinical granulomatous disease in humans without a deliberate immunizing event.

Decision criterion

The mouse model's translational validity would be supported if anti-vimentin immunity and the restricted clone arise spontaneously before human disease onset and endogenous vimentin nucleates granulomas without artificial immunization/bead challenge; it would be undercut if anti-vimentin responses are only a downstream consequence of established granulomatous tissue damage.

Show evidence (1 reference)

PMID:35434591 SUPPORT Model Organism

"Vimentin-immunized mice developed lung granulomas following intravenous challenge with vimentin-coated beads."

The causal mouse result whose translational validity to spontaneous human sarcoidosis this HUMAN_MODEL_MISMATCH discussion frames as the open question - it requires deliberate immunization and bead challenge.

⚙

Pathophysiology

Genetic Susceptibility

Sarcoidosis is a polygenic immune disorder. Risk-associated variants in HLA class II (DRB1 lineages), the truncating splice variant rs2076530 in BTNL2 (a T-cell co-inhibitory butyrophilin-like immunoglobulin superfamily member), the missense ANXA11 R230C (rs1049550), NOTCH4, and IL27RA collectively shift antigen presentation, T-cell co-stimulation/inhibition, and macrophage apoptosis thresholds, predisposing to exaggerated granulomatous response on antigen encounter.

Antigen Persistence / Th17.1 / mTORC1 Granuloma Chronicity Model Vimentin Autoantigen / HLA-DRB1*03 Autoimmunity Model

CD4-positive helper T cell CL:0000492

antigen processing and presentation GO:0019882

Downstream

Antigen Recognition and CD4+ T-Cell Activation Risk alleles in HLA-DRB1 and BTNL2 alter MHC class II antigen presentation and T-cell co-inhibition, lowering the threshold for an exaggerated CD4+ T-cell response to a triggering antigen.

Self-Antigen Vimentin Presentation by HLA-DRB1*03 In the vimentin autoimmunity model specifically, the HLA-DRB1*03 risk allele presents the self-peptide vimentin (Vim)429-443 to the restricted Valpha2.3/Vbeta22 CD4+ T-cell repertoire - the model-distinguishing self-antigen presentation step.

Show evidence (3 references)

PMID:15735647 SUPPORT Human Clinical

"The G --> A transition constituting rs2076530 leads to the use of a cryptic splice site located 4 bp upstream of the affected wild-type donor site. Transcripts of the risk-associated allele have a premature stop in the spliced mRNA. The resulting protein lacks the C-terminal IgC domain and..."

This case-control SNP scan identifies the truncating BTNL2 splice variant rs2076530 as a sarcoidosis risk factor independent of HLA-DRB1, with a defined molecular consequence (loss of membrane-anchored co-inhibitory protein).

PMID:19165924 SUPPORT Human Clinical

"The strongest association signal maps to the ANXA11 (annexin A11) gene on chromosome 10q22.3."

GWAS plus replication establishes ANXA11 as a major sarcoidosis susceptibility locus; the lead missense R230C (rs1049550) variant defined in this work is the molecular entry point for the apoptosis/proliferation arm of the pathograph.

PMID:19165924 PARTIAL Human Clinical

"Annexin A11 has complex and essential functions in several biological pathways, including apoptosis and proliferation."

Functional context for why ANXA11 risk variants are mechanistically relevant - the gene regulates apoptosis and proliferation, which are precisely the macrophage processes dysregulated in granuloma maintenance.

Self-Antigen Vimentin Presentation by HLA-DRB1*03

Vimentin-specific arm of antigen presentation (the step that distinguishes the vimentin autoimmunity model from the persistent-microbial-antigen model): HLA-DRB1*03 presents the self-peptide vimentin (Vim)429-443 (DSLPLVDTHSKRTLL) to a public, clonally restricted Valpha2.3/Vbeta22 CD4+ T-cell receptor repertoire found in the lungs of essentially all HLA-DRB1*03+ patients, with molecular modelling supporting a precise fit of the peptide to both the HLA cleft and the restricted TCR.

Vimentin Autoantigen / HLA-DRB1*03 Autoimmunity Model

alveolar macrophage CL:0000583 CD4-positive helper T cell CL:0000492

antigen processing and presentation of peptide antigen via MHC class II GO:0002495

Downstream

Antigen Recognition and CD4+ T-Cell Activation HLA-DRB1*03-presented vimentin peptide is recognized by the restricted Valpha2.3/Vbeta22 CD4+ T cells, feeding the shared antigen-recognition and Th17.1 effector chain.

Show evidence (3 references)

PMID:26585430 SUPPORT Computational

"Molecular modelling revealed specific T-cell receptor-HLA-DRB1*03-peptide interactions, with a previously identified, sarcoidosis-associated vimentin peptide, (Vim)429-443 DSLPLVDTHSKRTLL, matching both the HLA peptide-binding cleft and distinct T-cell receptor features perfectly."

Molecular modelling supports HLA-DRB1*03 presentation of the vimentin Vim429-443 peptide to the restricted TCR, the self-antigen presentation step unique to this model.

PMID:26585430 SUPPORT Human Clinical

"Simultaneous expression of Vα2.3 with the Vβ22 chain was identified in the lungs of all HLA-DRB1*03(+) patients."

Documents the restricted Valpha2.3/Vbeta22 CD4+ T-cell repertoire in the lungs of HLA-DRB1*03+ patients that recognizes the presented vimentin peptide.

PMID:17975675 SUPPORT Human Clinical

"We identified 78 amino acid sequences from self proteins presented in the lungs of sarcoidosis patients, some of which were well-known autoantigens such as vimentin and ATP synthase."

Direct physical-presentation evidence - acid-eluted HLA-DR peptides from DRB1*0301+ patient BAL cells include vimentin, substantiating the presentation step beyond molecular modelling (and consistent with the multi-antigen milieu, since ATP synthase is co-presented).

Antigen Recognition and CD4+ T-Cell Activation

Susceptibility alleles permit MHC class II presentation of candidate microbial or self peptides to CD4+ T cells, which expand clonally and may acquire a Th1/Th17.1 effector program with high IFN-gamma production. Bioaerosols or inorganic particles could instead supply antigenic material, generate modified-self epitopes, or act through innate or adjuvant pathways, but their route to HLA-restricted T-cell activation remains unresolved.

Antigen Persistence / Th17.1 / mTORC1 Granuloma Chronicity Model Vimentin Autoantigen / HLA-DRB1*03 Autoimmunity Model

CD4-positive helper T cell CL:0000492 alveolar macrophage CL:0000583

antigen processing and presentation of peptide antigen via MHC class II GO:0002495 T cell activation GO:0042110

Downstream

Th17.1 Polarization and IFN-gamma Production Antigen-activated CD4+ T cells in lung tissue polarize toward an IFN-gamma-producing Th17.1 phenotype that drives sustained granulomatous inflammation.

Show evidence (2 references)

PMID:21092305 SUPPORT Human Clinical

"Alveolar T-cells from twenty-two of the 31 sarcoidosis patients produced a CD4+ response to at least one of ESAT-6, katG, Ag85A, sodA, or HSP, compared to two of 14 PPD- controls (p = 0.0008)"

Direct demonstration that lung-resident T cells from sarcoidosis patients recognize mycobacterial antigens, supporting an antigen-driven step linking the susceptibility node to T-cell activation.

PMID:31273209 SUPPORT Other

"The typical T cell accumulation, local T cell immune response and granuloma formation in the lungs indicate that the inflammatory response in sarcoidosis is induced by specific antigens, possibly including self-antigens, which is consistent with an autoimmune involvement."

Review-level synthesis supports antigen-driven local T-cell responses in pulmonary sarcoidosis while preserving uncertainty about antigen identity.

Th17.1 Polarization and IFN-gamma Production

Plasticity within the Th17 lineage produces IFN-gamma-producing Th17.1 cells that are the dominant source of IFN-gamma in pulmonary sarcoidosis and correlate with progressive (non-Lofgren) disease. Concurrent Treg dysfunction (impaired survival, altered CTLA-4 expression) removes the brake on this effector response.

Antigen Persistence / Th17.1 / mTORC1 Granuloma Chronicity Model

T-helper 17 cell CL:0000899 regulatory T cell CL:0000815

T-helper 17 type immune response GO:0072538 regulatory T cell apoptotic process GO:1902482

Downstream

Macrophage Activation and mTORC1 Hyperactivation IFN-gamma-rich Th17.1 inflammation, persistent antigen, and other tissue signals are hypothesized to converge on recruitment, activation, and metabolic reprogramming of macrophages; direct Th17.1-to-macrophage mTORC1 causality in human sarcoidosis remains unproven.

Show evidence (4 references)

PMID:27379969 SUPPORT Other

"it was demonstrated that Th17.1-cells rather than Th1-cells are responsible for the exaggerated IFN-γ production in pulmonary sarcoidosis."

Reviews the paradigm shift identifying Th17.1 cells (not classical Th1) as the dominant IFN-gamma source in sarcoidosis, anchoring this node mechanistically.

PMID:29310925 SUPPORT Other

"In non-LS sarcoidosis patients, IFN-γ-producing Th17.1-cells appear to be more pathogenic and possibly linked to disease progression"

Direct support that Th17.1 polarization marks the pathogenic, progression-prone arm of sarcoidosis and is the upstream effector that drives macrophage transformation.

PMID:24882950 SUPPORT Human Clinical

"The proportion of Th17 cells positive for IFN-gamma was greater in sarcoidosis than controls (median 72.4% versus 31%, P = 0.0005) and increased with radiologic stage (N = 23, rho = 0.45, and P = 0.03)."

Quantitative evidence that the IFN-gamma+ Th17 (Th17.1) compartment is enriched in lung lavage of sarcoidosis patients and tracks with radiographic stage.

+ 1 more reference

Macrophage Activation and mTORC1 Hyperactivation

Chronic antigenic stimulation drives macrophage hypertrophy, proliferation, and transformation into epithelioid cells. A macrophage-intrinsic increase in mTORC1 signaling (genetically modeled by Tsc2 deletion) is sufficient to initiate and sustain non-caseating granulomas, via CDK4-dependent proliferation, glycolytic reprogramming, and suppression of macrophage apoptosis. mTORC1 activation is enriched in progressive human sarcoidosis lesions.

Antigen Persistence / Th17.1 / mTORC1 Granuloma Chronicity Model

epithelioid macrophage CL:0002150 macrophage CL:0000235

TORC1 signaling GO:0038202 ↑ INCREASED macrophage activation GO:0042116 glycolytic process GO:0006096 ↑ INCREASED pentose-phosphate shunt GO:0006098 ↑ INCREASED negative regulation of macrophage apoptotic process GO:2000110

Downstream

Granuloma Formation mTORC1-driven hypertrophic, proliferating macrophages aggregate with multinucleated giant cells and CD4+ T cells to form non-caseating granulomas.

Show evidence (4 references)

PMID:28092373 SUPPORT Model Organism

"We found that activation of the metabolic checkpoint kinase mTORC1 in macrophages by deletion of the gene encoding tuberous sclerosis 2 (Tsc2) was sufficient to induce hypertrophy and proliferation, resulting in excessive granuloma formation in vivo."

Conditional Tsc2 deletion in mouse myeloid cells is sufficient to recapitulate sarcoid-like granulomas, mechanistically anchoring macrophage-intrinsic mTORC1 hyperactivation as a granuloma-initiating step.

PMID:28092373 SUPPORT Human Clinical

"In human sarcoidosis patients, mTORC1 activation, macrophage proliferation and glycolysis were identified as hallmarks that correlated with clinical disease progression."

Re-analysis of human sarcoidosis biopsies translates the mouse mechanism - mTORC1 activity, macrophage proliferation, and glycolysis distinguish progressive from self-limiting disease in patients.

PMID:29104468 PARTIAL Human Clinical

"Disturbance of T memory cells, Th1/Th2, and Tregs/Th17 cells, and activation of PI3K/Akt signaling were seen in newly diagnosed stage II pulmonary sarcoidosis"

Independent confirmation that PI3K/Akt (upstream of mTORC1) is activated in pulmonary sarcoidosis BAL cells, supporting parallel relevance of this metabolic axis in human disease.

+ 1 more reference

Granuloma Formation

Non-caseating granulomas consist of organized collections of activated macrophages (epithelioid cells), multinucleated giant cells, and CD4+ T cells. Th1/Th17.1 immune responses drive granuloma development in response to persistent antigens. Granulomas are the defining histopathologic lesion that mediates the downstream organ-level phenotypes of sarcoidosis. This node conforms to the conserved granuloma-formation module: sarcoid granulomas are characteristically non-caseating, distinguishing them from the caseating granulomas of tuberculosis.

Antigen Persistence / Th17.1 / mTORC1 Granuloma Chronicity Model

epithelioid macrophage CL:0002150 multinucleated giant cell CL:0000647 CD4-positive helper T cell CL:0000492

granuloma formation GO:0002432 Macrophage fusion into multinucleated giant cells GO:0000768 ↑ INCREASED

Downstream

Macrophage Calcitriol Production Granuloma macrophages express CYP27B1 and convert 25-hydroxyvitamin D to active 1,25-dihydroxyvitamin D outside normal renal regulation, predisposing to hypercalcemia.

Macrophage ACE Production Epithelioid macrophages within granulomas synthesize angiotensin-converting enzyme, producing the elevated serum ACE characteristic of active sarcoidosis.

Fibrotic Tissue Remodeling Persistent granulomatous inflammation is associated with later TGF-beta-driven myofibroblast programs and excessive ECM deposition in a subset of patients, but the switch from active granulomas to fibrotic remodeling is not resolved and may involve partly distinct profibrotic pathways.

Show evidence (3 references)

PMID:35011621 PARTIAL Other

"Sarcoidosis is a chameleon disease of unknown etiology, characterized by the growth of non-necrotizing and non-caseating granulomas"

This review confirms the characteristic non-caseating granuloma formation in sarcoidosis.

PMID:38165044 SUPPORT Other

"Sarcoidosis is a complex immune-mediated disease characterized by clusters of immune cells called granulomas."

This 2024 JCI mechanistic review frames sarcoidosis as a granuloma-defined immune-mediated disease and is the source for the integrated antigen-T-cell-macrophage causal chain summarized here.

PMID:33329511 SUPPORT Other

"The sarcoidosis granuloma is formed by a distinct conglomeration of multinucleated giant cells and epithelioid macrophages surrounded by a rim of CD4+ T cells"

Full-text review-level support for the core immune-cell architecture of sarcoid granulomas: macrophage-lineage giant/epithelioid cells surrounded by CD4+ T cells.

Macrophage Calcitriol Production

Activated monocytes and macrophages within sarcoid granulomas express 1-alpha-hydroxylase (CYP27B1), converting 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D outside normal PTH/FGF23 regulation. This extrarenal calcitriol synthesis, with optional PTHrP secretion, drives intestinal calcium absorption and bone resorption, producing hypercalcemia and hypercalciuria.

macrophage CL:0000235

vitamin D metabolic process GO:0042359 ↑ INCREASED

Downstream

Hypercalcemia Extrarenal 1,25-dihydroxyvitamin D production by granuloma macrophages causes hypercalcemia in approximately 5-10% of patients.

Show evidence (2 references)

PMID:24663253 SUPPORT Human Clinical

"Hypercalcemia in sarcoidosis is due to three mechanistic reasons: (1) systemic conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by the enzyme 1-alpha hydroxylase produced by activated monocyte/macrophage system, (2) production of parathormone-related peptide (PTHrP) by the sarcoid..."

Mechanistic case-based report explicitly attributing sarcoid hypercalcemia to macrophage-driven extrarenal CYP27B1 expression and PTHrP, defining the molecular bridge from granuloma to the hypercalcemia phenotype.

PMID:23337133 SUPPORT Human Clinical

"Hypercalcemia associated with mineral oil induced skin lesions is likely driven by unregulated expression of CYP27b1 by inflammatory monocytes and macrophages infiltrating the dermis."

A non-sarcoidosis granulomatous condition independently demonstrates that ectopic CYP27B1 expression in tissue macrophages causes hypercalcemia, generalizing the macrophage-calcitriol mechanism.

Macrophage ACE Production

Epithelioid macrophages within granulomas constitutively express angiotensin-converting enzyme (ACE), and serum ACE elevation reflects total granuloma burden. Single-cell RNA-seq of cutaneous sarcoid granulomas has identified TREM2-positive ACE-expressing macrophages as a granuloma-resident population, supporting macrophage origin of the serum biomarker.

epithelioid macrophage CL:0002150

Downstream

Elevated ACE Granuloma-resident epithelioid macrophages secrete ACE; circulating levels are raised in active sarcoidosis and broadly correlate with granuloma burden.

Show evidence (1 reference)

PMID:38038136 SUPPORT Human Clinical

"the percentages of triggering receptor expressed on myeloid cells 2-positive (TREM2-positive) macrophages expressing angiotensin-converting enzyme (ACE) and lysozyme, diagnostic makers of sarcoidosis, were increased in cutaneous sarcoidosis granulomas."

Single-cell RNA-seq demonstrates TREM2+ macrophages expressing ACE are enriched in sarcoid granulomas, directly supporting the macrophage origin of serum ACE elevation.

Fibrotic Tissue Remodeling

In approximately 10-30% of patients with chronic disease, persistent granulomatous inflammation transitions to a profibrotic state characterized by TGF-beta signaling, fibroblast/myofibroblast activation, and excessive extracellular matrix deposition. The end result is irreversible parenchymal fibrosis with restrictive physiology, fibrocystic remodeling, and respiratory failure. This node conforms to the conserved fibrotic response module.

fibroblast CL:0000057

extracellular matrix organization GO:0030198 ↑ INCREASED

Downstream

Pulmonary Fibrosis Persistent granulomatous inflammation drives ECM deposition, restrictive physiology, and irreversible fibrocystic remodeling in 10-30% of patients.

Show evidence (1 reference)

PMID:41095908 SUPPORT Human Clinical

"Although many patients experience spontaneous remission, approximately 10-30% develop progressive pulmonary disease, which may lead to fibrocystic changes, respiratory failure, and death."

This review directly supports progression from pulmonary sarcoidosis to fibrocystic and fibrotic lung disease in a substantial subset of patients.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

Blood 2

Thrombocytopenia FREQUENT Thrombocytopenia HP:0001873

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0001873 | Thrombocytopenia | Frequent (79-30%)"

Orphanet records thrombocytopenia as a frequent (30-79%) phenotype of sarcoidosis.

Leukopenia FREQUENT Decreased total leukocyte count HP:0001882

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0001882 | Leukopenia | Frequent (79-30%)"

Orphanet records leukopenia as a frequent (30-79%) phenotype of sarcoidosis.

Cardiovascular 8

Mediastinal Lymphadenopathy VERY_FREQUENT Mediastinal lymphadenopathy HP:0100721

Show evidence (1 reference)

PMID:31485575 PARTIAL Human Clinical

"Although intrathoracic involvement is the hallmark of the disease, present in over 90% of patients, sarcoidosis can affect virtually any organ."

This Mayo Clinic review strongly supports intrathoracic involvement as the dominant manifestation of sarcoidosis, but only indirectly supports mediastinal lymphadenopathy specifically.

Atrioventricular Block OCCASIONAL Atrioventricular block HP:0001678

Show evidence (1 reference)

PMID:39621157 SUPPORT Human Clinical

"male gender, a QRS duration > 120 ms, and nsVT on Holter monitoring were identified as significant markers associated with the presence of cardiac sarcoidosis"

Cohort screening study supports conduction abnormalities (QRS >120 ms, including AV block) as defining cardiac sarcoidosis features.

Ventricular Arrhythmia OCCASIONAL Ventricular arrhythmia HP:0004308

Show evidence (1 reference)

PMID:39621157 SUPPORT Human Clinical

"Early detection of cardiac sarcoidosis (CS) is crucial due to its association with severe complications such as ventricular arrhythmias, heart failure, and sudden cardiac death."

Directly supports ventricular arrhythmia as a recognized cardiac sarcoidosis complication.

Sudden Cardiac Death OCCASIONAL Sudden cardiac death HP:0001645

Show evidence (1 reference)

PMID:39621157 SUPPORT Human Clinical

"Early detection of cardiac sarcoidosis (CS) is crucial due to its association with severe complications such as ventricular arrhythmias, heart failure, and sudden cardiac death."

Directly supports sudden cardiac death as a severe sarcoidosis complication driven by myocardial granulomatous involvement.

Hepatosplenomegaly OCCASIONAL Hepatosplenomegaly HP:0001433

Show evidence (2 references)

PMID:30305603 SUPPORT Human Clinical

"The majority of patients with hepatic sarcoidosis are usually asymptomatic, with only 5-30% presenting with abdominal pain, jaundice, nausea, vomiting, and hepatosplenomegaly."

Directly supports hepatosplenomegaly as a clinical manifestation of hepatic sarcoidosis occurring in 5-30% of affected patients.

PMID:11734441 SUPPORT Human Clinical

"Black subjects were more likely to have skin involvement other than erythema nodosum (chi(2) = 5.47, p < 0.05), and eye (chi(2) = 13.8, p < 0.0001), liver (chi(2) = 23.3, p < 0.0001), bone marrow (chi(2) = 18.8, p < 0.001), and extrathoracic lymph node involvement (chi(2) = 7.21, p < 0.01)."

ACCESS cohort demonstrates liver involvement as a recognized organ manifestation of sarcoidosis with racial differences in frequency.

Splenomegaly OCCASIONAL Splenomegaly HP:0001744

Show evidence (1 reference)

PMID:30305603 SUPPORT Human Clinical

"The majority of patients with hepatic sarcoidosis are usually asymptomatic, with only 5-30% presenting with abdominal pain, jaundice, nausea, vomiting, and hepatosplenomegaly."

Hepatosplenomegaly directly supports splenomegaly as a clinical manifestation in hepatic sarcoidosis patients.

Peripheral Lymphadenopathy OCCASIONAL Lymphadenopathy HP:0002716

Show evidence (2 references)

PMID:11734441 SUPPORT Human Clinical

ACCESS cohort study directly demonstrates extrathoracic lymph node involvement as a recognized manifestation of sarcoidosis.

ORPHA:797 SUPPORT

"peripheral lymph nodes, fatigue, weight loss, fever or night sweats"

Orphanet definition lists peripheral lymph nodes as a typical presentation feature.

Heart Failure OCCASIONAL Congestive heart failure HP:0001635

Show evidence (2 references)

PMID:39621157 SUPPORT Human Clinical

"Early detection of cardiac sarcoidosis (CS) is crucial due to its association with severe complications such as ventricular arrhythmias, heart failure, and sudden cardiac death."

Heart failure directly supported as a severe complication of cardiac sarcoidosis.

PMID:27454307 SUPPORT Human Clinical

"arrhythmias and heart failure in cardiac sarcoidosis"

Heart failure confirmed as an organ-specific manifestation of cardiac sarcoidosis.

Digestive 1

Decreased liver function FREQUENT Decreased liver function HP:0001410

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0001410 | Decreased liver function | Frequent (79-30%)"

Orphanet records decreased liver function as a frequent (30-79%) phenotype of sarcoidosis.

Endocrine 1

Diabetes insipidus OCCASIONAL Diabetes insipidus HP:0000873

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0000873 | Diabetes insipidus | Occasional (29-5%)"

Orphanet records diabetes insipidus as an occasional (5-29%) phenotype of sarcoidosis.

Eye 4

Uveitis OCCASIONAL Uveitis HP:0000554

Show evidence (1 reference)

PMID:33173272 SUPPORT Human Clinical

"Uveitis was the most common ocular manifestation."

This retrospective series directly supports uveitis as a common ocular manifestation among patients with ocular sarcoidosis.

Glaucoma OCCASIONAL Glaucoma HP:0000501

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0000501 | Glaucoma | Occasional (29-5%)"

Orphanet records glaucoma as an occasional (5-29%) phenotype of sarcoidosis.

Cataract OCCASIONAL Cataract HP:0000518

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0000518 | Cataract | Occasional (29-5%)"

Orphanet records cataract as an occasional (5-29%) phenotype of sarcoidosis.

Blindness OCCASIONAL Blindness HP:0000618

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0000618 | Blindness | Occasional (29-5%)"

Orphanet records blindness as an occasional (5-29%) phenotype of sarcoidosis.

Genitourinary 2

Renal insufficiency OCCASIONAL Renal insufficiency HP:0000083

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0000083 | Renal insufficiency | Occasional (29-5%)"

Orphanet records renal insufficiency as an occasional (5-29%) phenotype of sarcoidosis.

Nephrolithiasis OCCASIONAL Nephrolithiasis HP:0000787

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0000787 | Nephrolithiasis | Occasional (29-5%)"

Orphanet records nephrolithiasis as an occasional (5-29%) phenotype of sarcoidosis.

Head and Neck 2

Facial Palsy OCCASIONAL Facial palsy HP:0010628

Show evidence (1 reference)

PMID:33110001 PARTIAL Human Clinical

"Sarcoidosis is an idiopathic, multisystem, inflammatory disease that has central nervous system involvement in 5%-15% of cases."

Establishes CNS involvement frequency in sarcoidosis; cranial neuropathies including facial palsy are recognized presenting features.

Dacryocystitis OCCASIONAL Dacryocystitis HP:0000620

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0000620 | Dacryocystitis | Occasional (29-5%)"

Orphanet records dacryocystitis as an occasional (5-29%) phenotype of sarcoidosis.

Immune 1

Erythema Nodosum OCCASIONAL Erythema nodosum HP:0012219

Show evidence (1 reference)

PMID:39082153 SUPPORT Human Clinical

"Löfgren syndrome (LS) is a sarcoidosis subtype characterised by an acute disease course, bilateral hilar lymphadenopathy (BHL), erythema nodosum (EN), and ankle arthritis."

This review of Lofgren syndrome directly supports erythema nodosum as a recognized acute cutaneous manifestation of sarcoidosis.

Integument 3

Lupus Pernio OCCASIONAL Skin plaque HP:0200035

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:30555667 SUPPORT Human Clinical

"LP is a rare presentation with infiltrated erythematoviolaceous plaques affecting the nose."

This case report and literature review directly identifies lupus pernio as a cutaneous sarcoidosis manifestation characterized by infiltrated violaceous plaques.

Skin nodule FREQUENT Skin nodule HP:0200036

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0200036 | Skin nodule | Frequent (79-30%)"

Orphanet records skin nodule as a frequent (30-79%) phenotype of sarcoidosis.

Hyperpigmentation of the skin OCCASIONAL Hyperpigmentation of the skin HP:0000953

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0000953 | Hyperpigmentation of the skin | Occasional (29-5%)"

Orphanet records hyperpigmentation of the skin as an occasional (5-29%) phenotype of sarcoidosis.

Metabolism 4

Hypercalcemia OCCASIONAL Hypercalcemia HP:0003072

Show evidence (1 reference)

PMID:24663253 SUPPORT Human Clinical

Directly supports hypercalcemia as a phenotype of sarcoidosis with a defined macrophage-CYP27B1 mechanism.

Fever OCCASIONAL Fever HP:0001945

Show evidence (2 references)

PMID:38227868 SUPPORT Human Clinical

"Patients with sarcoidosis can exhibit constitutional symptoms such as fever, unintentional weight loss, and fatigue."

Fever listed as a recognized constitutional symptom of sarcoidosis.

ORPHA:797 SUPPORT

"Clinical presentation is typically with persistent dry cough, eye or skin manifestations, peripheral lymph nodes, fatigue, weight loss, fever or night sweats, and Löfgren syndrome."

Orphanet definition includes fever as a typical clinical presentation feature.

Joint swelling FREQUENT Joint swelling HP:0001386

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0001386 | Joint swelling | Frequent (79-30%)"

Orphanet records joint swelling as a frequent (30-79%) phenotype of sarcoidosis.

Pleural effusion FREQUENT Pleural effusion HP:0002202

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0002202 | Pleural effusion | Frequent (79-30%)"

Orphanet records pleural effusion as a frequent (30-79%) phenotype of sarcoidosis.

Nervous System 1

Small Fiber Neuropathy FREQUENT Peripheral neuropathy HP:0009830

Show evidence (2 references)

PMID:39291161 SUPPORT Human Clinical

"Small fiber neuropathy is a common complication in patients with sarcoidosis and its prevalence is estimated at 40-86%."

Establishes small fiber neuropathy as a highly prevalent complication of sarcoidosis.

PMID:24090799 SUPPORT Human Clinical

"Recognition of unexplained persistent disabling symptoms, fatigue, small-fibre neurological impairment, cognitive failure, and changes to health state and quality of life, has improved."

Lancet review recognizes small-fiber neurological impairment as an important persistent disabling symptom of sarcoidosis.

Respiratory 4

Dyspnea FREQUENT Dyspnea HP:0002094

Show evidence (1 reference)

PMID:38227868 SUPPORT Human Clinical

"Ongoing dyspnea and dry cough in a young to middle-aged adult should increase the suspicion for sarcoidosis."

This 2024 American Family Physician review identifies dyspnea as a key presenting symptom that should raise suspicion for sarcoidosis.

Nonproductive Cough FREQUENT Nonproductive cough HP:0031246

Show evidence (1 reference)

PMID:38227868 SUPPORT Human Clinical

"Ongoing dyspnea and dry cough in a young to middle-aged adult should increase the suspicion for sarcoidosis."

Dry cough is identified as a hallmark symptom that should raise clinical suspicion for sarcoidosis in younger adults.

Pulmonary Fibrosis OCCASIONAL Pulmonary fibrosis HP:0002206

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:41095908 SUPPORT Human Clinical

"Although many patients experience spontaneous remission, approximately 10-30% develop progressive pulmonary disease, which may lead to fibrocystic changes, respiratory failure, and death."

Directly supports pulmonary fibrosis as a progression-related phenotype occurring in a substantial subset of sarcoidosis patients.

Cough FREQUENT Cough HP:0012735

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0012735 | Cough | Frequent (79-30%)"

Orphanet records cough as a frequent (30-79%) phenotype of sarcoidosis.

Constitutional 4

Fatigue FREQUENT Fatigue HP:0012378

Show evidence (1 reference)

PMID:38227868 PARTIAL Human Clinical

"Patients with sarcoidosis can exhibit constitutional symptoms such as fever, unintentional weight loss, and fatigue."

This review supports fatigue as a recognized constitutional symptom in sarcoidosis, but the wording is not strong enough on its own to justify a VERY_FREQUENT frequency assignment.

Arthralgia FREQUENT Arthralgia HP:0002829

Show evidence (2 references)

PMID:38281070 SUPPORT Human Clinical

"The PPE for sarcoid arthritis (SA) was 19% (95% CI 14, 24; I2 = 95%), and 32% (95% CI 13, 51; I2 = 99%) for arthralgia."

Systematic review and meta-analysis of 49 studies (8574 patients) establishes arthralgia pooled prevalence at 32% and sarcoid arthritis at 19%.

PMID:27454307 SUPPORT Human Clinical

"Systemic symptoms include fatigue, night sweats, weight loss, fever, arthralgia and myalgia."

Epidemiologic review listing arthralgia as a recognized systemic symptom of sarcoidosis.

Night Sweats OCCASIONAL Night sweats HP:0030166

Show evidence (2 references)

PMID:27454307 SUPPORT Human Clinical

"Systemic symptoms include fatigue, night sweats, weight loss, fever, arthralgia and myalgia."

Night sweats listed among systemic symptoms of sarcoidosis.

ORPHA:797 SUPPORT

"fatigue, weight loss, fever or night sweats, and Löfgren syndrome."

Orphanet definition includes night sweats in typical presentation.

Chest Pain FREQUENT Chest pain HP:0100749

Show evidence (1 reference)

PMID:31273209 SUPPORT Other

"Patients frequently suffer from cough, shortness of breath, chest pain and pronounced fatigue"

Nature Reviews Disease Primers identifies chest pain as a frequent symptom of sarcoidosis.

Growth 1

Weight Loss OCCASIONAL Weight loss HP:0001824

Show evidence (2 references)

PMID:38227868 SUPPORT Human Clinical

"Patients with sarcoidosis can exhibit constitutional symptoms such as fever, unintentional weight loss, and fatigue."

Weight loss identified as a constitutional symptom of sarcoidosis.

ORPHA:797 SUPPORT

"Clinical presentation is typically with persistent dry cough, eye or skin manifestations, peripheral lymph nodes, fatigue, weight loss, fever or night sweats, and Löfgren syndrome."

Orphanet definition lists weight loss as a typical presentation feature.

Other 2

Nephrocalcinosis OCCASIONAL Nephrocalcinosis HP:0000121

Show evidence (1 reference)

PMID:35436276 SUPPORT Human Clinical

"Glomerulopathies, nephrocalcinosis and nephrolithiasis are among the most commonly seen types of renal involvement."

Directly names nephrocalcinosis among the most common types of renal involvement in sarcoidosis; the same source reports renal involvement in ~30% of cases.

Increased T cell count FREQUENT Increased total T cell count HP:0100828

Show evidence (1 reference)

ORPHA:797 SUPPORT Other

"HP:0100828 | Increased T cell count | Frequent (79-30%)"

Orphanet records increased T cell count as a frequent (30-79%) phenotype of sarcoidosis.

🧬

Genetic Associations

HLA-DRB1 Variants (Susceptibility)

Gene: HLA-DRB1 hgnc:4948

Show evidence (1 reference)

PMID:25506722 SUPPORT Human Clinical

"This study has identified DRB1*03:01 and *03:02 as novel alleles associated with disease susceptibility and course in African Americans."

This large genetic association study directly supports HLA-DRB1 variation as a determinant of sarcoidosis susceptibility and clinical course.

BTNL2 Variants (Susceptibility)

Gene: BTNL2 hgnc:1142

Show evidence (2 references)

PMID:21410903 SUPPORT Human Clinical

"The BTNL2 A allele variant occurs with a high frequency in Danish patients with sarcoidosis and the AA genotype is associated with a ~threefold higher risk of sarcoidosis than the GG genotype."

This case-control study directly supports BTNL2 variation as a sarcoidosis susceptibility factor.

PMID:15735647 SUPPORT Human Clinical

Defines the molecular consequence - the A risk allele creates a cryptic splice site producing a truncated BTNL2 protein lacking the membrane anchor, reducing T-cell co-inhibitory signalling.

ANXA11 Variants (Susceptibility)

Gene: ANXA11 hgnc:535

Show evidence (3 references)

PMID:19165924 SUPPORT Human Clinical

"The strongest association signal maps to the ANXA11 (annexin A11) gene on chromosome 10q22.3."

Original GWAS implicating ANXA11 as a sarcoidosis susceptibility locus.

PMID:32552203 SUPPORT Human Clinical

"It also confirms previously reported 'protective' association between sarcoidosis and functional variant ANXA11 rs1049550*A."

Independent replication in a Greek cohort confirms the protective association of the ANXA11 rs1049550 A allele, reinforcing the locus.

PMID:29416296 SUPPORT Human Clinical

"SNPs rs1040461 and rs61860052, in ras-related protein RAS23 (RAB23) and annexin A11 (ANXA11) genes, respectively, were associated with sarcoidosis-associated uveitis."

Subgroup analysis links ANXA11 variation specifically to the uveitis phenotype, providing a genotype-phenotype edge from genetic susceptibility to ocular manifestation.

NOTCH4 Variants (Susceptibility)

Gene: NOTCH4 hgnc:7884

Show evidence (1 reference)

PMID:22952805 SUPPORT Human Clinical

"We identified a novel sarcoidosis-associated locus, NOTCH4, that reached genome-wide significance in the combined AA samples (rs715299, P(AA-meta) = 6.51 × 10(-10)) and demonstrated the independence of this locus from others in the MHC region in the same sample."

GWAS in African Americans identifies NOTCH4 as a genome-wide significant sarcoidosis susceptibility locus independent of other MHC loci.

IL27RA Variants (Susceptibility)

Gene: IL27RA hgnc:17290

Show evidence (1 reference)

PMID:31273209 PARTIAL Other

"Genetic factors affect not only the risk of developing sarcoidosis but also the disease course, which is highly variable and difficult to predict."

Nature Reviews Disease Primers review supports a polygenic contribution to sarcoidosis susceptibility including cytokine receptor variants; IL27RA is one of the implicated loci.

TSC2 / mTORC1 Pathway (Mechanistic)

Gene: TSC2 hgnc:12363

Show evidence (1 reference)

PMID:28092373 SUPPORT Model Organism

"TSC2-deficient macrophages formed mTORC1-dependent granulomatous structures in vitro and showed constitutive proliferation that was mediated by the neo-expression of cyclin-dependent kinase 4 (CDK4)."

Defines the molecular mechanism by which TSC2 loss in macrophages activates mTORC1 and induces CDK4-driven granulomatous proliferation, the macrophage-intrinsic engine of sarcoid granuloma maintenance.

💊

Medical Actions

Corticosteroid Therapy

Action: Systemic Corticosteroid Therapy NCIT:C122080

First-line treatment for symptomatic sarcoidosis. Prednisone typically initiated at 20-40mg daily with gradual taper over months. Effective for most organ manifestations.

Show evidence (2 references)

PMID:31485575 SUPPORT Human Clinical

"Glucocorticoids are the cornerstone of treatment of sarcoidosis even though evidence from randomized controlled studies is lacking."

This Mayo Clinic review establishes glucocorticoids as the cornerstone of sarcoidosis treatment.

PMID:38227868 SUPPORT Human Clinical

"Corticosteroids are the initial treatment for active disease, with refractory cases often requiring immunosuppressive or biologic therapies."

This 2024 review confirms corticosteroids as first-line initial treatment for active sarcoidosis.

Methotrexate

Action: immunosuppressive therapy Ontology label: Immunosuppressive Therapy NCIT:C15261

Agent: methotrexate CHEBI:44185

Most commonly used steroid-sparing agent for chronic sarcoidosis. Allows reduction of corticosteroid dose while maintaining disease control. The PREDMETH trial (NEJM 2025) demonstrated noninferiority of methotrexate to prednisone for 24-week change in % predicted FVC, supporting methotrexate as a first-line option in selected patients.

Mechanism Target:

INHIBITS Th17.1 Polarization and IFN-gamma Production — Methotrexate suppresses pathogenic Th17/Th17.1 effector responses central to granuloma maintenance.

Show evidence (2 references)

PMID:41095908 SUPPORT Human Clinical

"Antimetabolites such as methotrexate, azathioprine, mycophenolate mofetil, and leflunomide are commonly used second-line therapies."

This evidence-based review directly supports methotrexate as a standard second-line steroid-sparing therapy in pulmonary sarcoidosis.

PMID:40387020 SUPPORT Human Clinical

"Methotrexate was noninferior to prednisone with regard to the primary end point, with an adjusted between-group difference of -1.17 percentage points (95% CI, -4.27 to 1.93)."

The PREDMETH NEJM 2025 noninferiority trial demonstrates methotrexate is noninferior to prednisone for FVC change in pulmonary sarcoidosis, supporting methotrexate as a viable first-line alternative.

Anti-TNF Therapy

Action: biologic therapy Ontology label: Immunotherapy NCIT:C15262

Agent: infliximab NCIT:C1789

Anti-TNF agents, particularly infliximab, are used for refractory sarcoidosis when corticosteroids and steroid-sparing agents are insufficient. Because TNF is a non-redundant amplifier of macrophage recruitment and granuloma maintenance, its neutralization impairs granuloma integrity - the granuloma-formation-module drug-target pattern. This benefit carries a class boxed warning for reactivation of latent tuberculosis, where TNF blockade dissolves protective granulomas.

Mechanism Target:

INHIBITS Macrophage Activation and mTORC1 Hyperactivation — TNF neutralization removes a non-redundant amplifier of macrophage recruitment and activation, impairing granuloma initiation and maintenance.

Show evidence (1 reference)

PMID:41095908 SUPPORT Human Clinical

"For refractory disease, particularly in those with metabolically active lesions on FDG-PET, anti-tumor necrosis factor (TNF) agents like infliximab may be effective but carry risks of serious adverse effects."

This evidence-based review directly supports anti-TNF therapy, especially infliximab, as an option for refractory sarcoidosis.

JAK Inhibitor Therapy

Action: Pharmacotherapy NCIT:C15986

Janus kinase inhibitors (tofacitinib, ruxolitinib) are emerging steroid-sparing options that target IFN-gamma/JAK-STAT signalling downstream of Th17.1 cells. Pilot studies in corticosteroid-dependent and cutaneous sarcoidosis report benefit; larger trials are ongoing.

Mechanism Target:

INHIBITS Th17.1 Polarization and IFN-gamma Production — JAK inhibitors block IFN-gamma/JAK-STAT signalling, attenuating the Th17.1-driven IFN-gamma feedback that sustains granulomatous inflammation.

Show evidence (1 reference)

PMID:33825964 SUPPORT Human Clinical

"In this proof-of-concept study, the addition of a JAK-inhibitor allowed 60% of patients with pulmonary sarcoidosis to successfully taper corticosteroids."

Open-label proof-of-concept trial (NCT03793439) demonstrates tofacitinib enables steroid tapering in corticosteroid-dependent pulmonary sarcoidosis, supporting JAK inhibitors as a steroid-sparing option.

mTOR Inhibitor Therapy (Investigational)

Action: Pharmacotherapy NCIT:C15986

Inhibition of mTORC1 with rapamycin/everolimus completely resolved granulomas in Tsc2-deficient mouse models and successful single-patient use of rapamycin has been reported. Currently investigational in human sarcoidosis but mechanistically targeted at the macrophage-intrinsic granuloma maintenance arm.

Mechanism Target:

INHIBITS Macrophage Activation and mTORC1 Hyperactivation — Rapamycin/everolimus directly inhibit the mTORC1 signalling that drives macrophage proliferation and granuloma maintenance.

Show evidence (1 reference)

PMID:28092373 SUPPORT Model Organism

"Inhibition of mTORC1 induced apoptosis and completely resolved granulomas in myeloid TSC2-deficient mice."

Pharmacologic mTORC1 inhibition resolves granulomas in a sarcoid-like animal model, providing the rationale for mTOR-targeted human therapy.

🌍

Environmental Factors

Occupational Exposures

Associations have been reported with silica, other inorganic dusts, metals, and related occupational dust exposures.

Show evidence (2 references)

PMID:35156713 SUPPORT Human Clinical

"Occupational exposures for which associations are strongest and most consistent are silica and other inorganic dusts, World Trade Center (WTC) dust, and metals."

This occupational case series review directly supports industrial dust and metal exposure as relevant environmental associations in sarcoidosis.

PMID:41963075 PARTIAL Other

"The results suggested that occupational silica, pesticides, mould/mildew and World Trade Center ((WTC) dust exposures were associated with increased odds of pulmonary sarcoidosis. Sensitivity analysis confirmed the robustness of the association for WTC dust and mould, whereas the risk associated..."

This systematic review and meta-analysis supports class-specific occupational associations while showing sensitivity to study quality and heterogeneity. It does not identify an initiating trigger mechanism.

Microbial Bioaerosol and Musty-Odor Work Environments

ACCESS found modest associations with reported mold/mildew or musty-odor work environments (adjusted OR 1.62, CI 1.24-2.11); these observations do not establish a specific organism, antigen, or causal exposure pathway.

Show evidence (1 reference)

PMID:15347561 PARTIAL Human Clinical

The matched ACCESS case-control study supports an association with reported microbial-bioaerosol work environments, not a causal bioaerosol species or mechanism.

Occupational Insecticide Exposure

ACCESS found a modest adjusted association with occupational insecticide exposure; questionnaire ascertainment and residual confounding limit causal interpretation.

Show evidence (2 references)

PMID:15347561 PARTIAL Human Clinical

The adjusted ACCESS estimate supports an epidemiologic association, not proof that insecticides initiate sarcoidosis or use a defined immune pathway.

PMID:30793815 PARTIAL Human Clinical

"We applied the proposed method to conduct a GEWIS of a known sarcoidosis risk factor (insecticide exposure) and risk of sarcoidosis in African Americans and identified two novel loci with suggestive evidence of G × E interaction."

This analysis identifies two suggestive insecticide-by-locus interaction leads in one African American study population. It does not establish insecticide causality, replicate the specific ACCESS HLA-exposure pairs, or define an immune pathway.

Agricultural Employment

Agricultural employment was associated with sarcoidosis in ACCESS (OR 1.46, CI 1.13-1.89), but the occupation aggregates heterogeneous chemical, dust, and bioaerosol exposures.

Show evidence (1 reference)

PMID:15347561 PARTIAL Human Clinical

"We identified several exposures associated with sarcoidosis risk, including insecticides, agricultural employment, and microbial bioaerosols."

The ACCESS association identifies agricultural employment as an exposure lead but does not resolve which correlated exposure, if any, is causal.

Cigarette Smoking History

Ever-smoking history was inversely associated with sarcoidosis in ACCESS. Separately, a Swedish case-control study reported subgroup-specific additive interactions between smoking and variants in FCRL1 in Löfgren syndrome and IL23R in non-Löfgren disease. This genotype-conditional signal is not equivalent to a marginal smoking effect; neither observational result establishes a causal protective or harmful effect of smoking.

Show evidence (2 references)

PMID:15347561 PARTIAL Human Clinical

"A history of ever smoking cigarettes was less frequent among cases than control subjects (OR 0.62, CI 0.50-0.77)."

ACCESS documents an inverse case-control association, which may reflect biological effects, selection, behavior change, or confounding and does not support recommending smoking.

PMID:31819081 PARTIAL Human Clinical

The FCRL1 and IL23R findings are genotype-conditional joint interaction signals from one cohort, not a marginal estimate like the inverse ACCESS association. They qualify interpretation of smoking history without establishing that smoking is protective or harmful across genotypes.

Infectious Triggers

Mycobacterial and propionibacterial antigens have been implicated as potential triggers

Show evidence (1 reference)

PMID:22596102 SUPPORT Human Clinical

"Mycobacterial and propionibacterial organisms are the most commonly implicated potential etiologic agents."

This pathology study directly supports mycobacterial and propionibacterial organisms as leading infectious candidates in sarcoidosis pathogenesis.

🔬

Biochemical Markers

Elevated ACE (Elevated)

Context: Serum angiotensin-converting enzyme often elevated but not specific for diagnosis

Show evidence (1 reference)

PMID:36778180 SUPPORT Human Clinical

"Raised angiotensin-converting enzyme (ACE) levels were found in 56.8% of patients."

This retrospective cohort directly supports frequent elevation of serum ACE in sarcoidosis while remaining compatible with its limited diagnostic specificity.

Hypercalcemia (Elevated)

Context: Due to ectopic 1,25-dihydroxyvitamin D (calcitriol) production by granuloma macrophages

Show evidence (1 reference)

PMID:24663253 SUPPORT Human Clinical

This case-based report explicitly supports hypercalcemia in sarcoidosis and ties it to macrophage-driven calcitriol dysregulation within granulomatous tissue.

Elevated Inflammatory Markers (Elevated)

Context: ESR and CRP may be elevated during active disease

Show evidence (1 reference)

PMID:32407763 PARTIAL Human Clinical

"In contrast, ESR and Hs-CRP emerges to be more sensitive markers of active CS."

This study directly supports ESR and CRP elevation in active cardiac sarcoidosis, partially supporting their broader use as inflammatory activity markers in sarcoidosis.

Elevated Soluble IL-2 Receptor (Elevated)

Context: Serum soluble interleukin-2 receptor (sIL-2R) is shed by activated T cells and reflects the Th1/Th17.1 activation that drives granulomatous inflammation. It serves as a marker of disease activity and outperforms serum ACE for establishing the diagnosis (sensitivity 88%, specificity 85% versus 62%/76% for ACE).

Show evidence (2 references)

PMID:31622413 SUPPORT Human Clinical

"The soluble interleukin 2 receptor (sIL-2R) has been proposed as a marker of disease activity in patients with sarcoidosis."

Establishes sIL-2R as a recognized activity biomarker in sarcoidosis, mechanistically linked to the activated T-cell compartment.

PMID:31622413 SUPPORT Human Clinical

"The sensitivity and specificity of serum soluble interleukin 2 receptor levels to detect sarcoidosis were 88% and 85%. The sensitivity and specificity of ACE were 62% and 76%."

Quantifies the superior diagnostic performance of sIL-2R over serum ACE in patients suspected of sarcoidosis.

Elevated BAL CD4/CD8 Ratio (Elevated)

Context: An elevated bronchoalveolar lavage (BAL) CD4/CD8 T-cell ratio reflects the lung-compartmentalized, oligoclonal CD4+ T-cell alveolitis of sarcoidosis. An elevated ratio (an optimal cutoff of 3.7 was reported in one comparative series, close to the classic >3.5 threshold) is a high-specificity supportive finding that helps distinguish sarcoidosis from tuberculosis, idiopathic pulmonary fibrosis, and other interstitial lung diseases, though sensitivity is limited.

Show evidence (1 reference)

PMID:39976519 SUPPORT Human Clinical

"Sarcoidosis exhibited a significantly higher CD4/CD8 ratio compared to those with TB, IPF, and Other-ILDs. An optimal cutoff value of 3.7 for the CD4/CD8 ratio in sarcoidosis with an area under the ROC curve (AUC) of 0.7%, had a specificity of 96.8%, and a sensitivity of 43.2%."

Demonstrates the BAL CD4/CD8 ratio as a high-specificity, low-sensitivity discriminator of sarcoidosis from other interstitial lung diseases.

{ }

Source YAML

click to show

name: Sarcoidosis
creation_date: '2026-01-13T07:11:10Z'
updated_date: '2026-04-30T12:00:00Z'
category: Immune
description: >
  Sarcoidosis is a multisystem inflammatory disease of unknown etiology characterized
  by the formation of non-caseating granulomas, most commonly affecting the lungs
  and lymph nodes. The leading model holds that genetically susceptible individuals
  (HLA-DRB1, BTNL2, ANXA11, NOTCH4, IL27RA risk alleles) mount an exaggerated
  CD4+ T-cell response to a poorly degradable antigen (mycobacterial KatG/ESAT-6,
  propionibacterial, or environmental dusts), driving Th1/Th17.1-skewed inflammation,
  IFN-gamma production, and macrophage transformation into epithelioid and
  multinucleated giant cells organized into granulomas. Macrophage-intrinsic
  mTORC1 hyperactivation sustains granuloma maintenance and correlates with
  progressive disease. The disease predominantly affects adults aged 20-40 years,
  with higher incidence in African Americans and Northern Europeans. Clinical
  presentation ranges from asymptomatic to severe organ dysfunction; while many
  cases resolve spontaneously, chronic progressive disease (10-30%) progresses to
  pulmonary fibrosis, cardiac, neurologic, ocular, or cutaneous involvement.
disease_term:
  preferred_term: sarcoidosis
  term:
    id: MONDO:0019338
    label: sarcoidosis
parents:
- Granulomatous Disease
- Immune-Mediated Disease
prevalence:
- population: Europe (Germany)
  measure_type: POINT_PREVALENCE
  prevalence_class: BAND_1_5_PER_10000
  rate_low: 44.0
  rate_high: 48.0
  percentage: 44-48 per 100,000
  evidence:
  - reference: PMID:27454307
    reference_title: "[Epidemiology and Clinical Presentation of Sarcoidosis]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In Germany, the incidence is estimated to be 10 per 100,000, and the prevalence 44-48 per 100,000."
    explanation: German epidemiologic data supporting European prevalence estimate.
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    snippet: "A rare multisystemic, autoinflammatory disorder of unknown etiology characterized by the formation of immune, non-caseating granulomas in any organ(s), leading to variable clinical symptoms and severity."
    explanation: Orphanet classifies sarcoidosis as a rare multisystemic autoinflammatory disorder.
inheritance:
- name: Polygenic susceptibility
  description: Sarcoidosis is not a Mendelian disorder but shows familial clustering with polygenic susceptibility (HLA-DRB1, BTNL2, ANXA11). Risk is increased in first-degree relatives.
  evidence:
  - reference: PMID:27454307
    reference_title: "[Epidemiology and Clinical Presentation of Sarcoidosis]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Familial clusters can occur."
    explanation: Familial clustering supports genetic predisposition without Mendelian inheritance.
has_subtypes:
- name: Pulmonary Sarcoidosis
  description: Most common form, affecting lungs and hilar lymph nodes; staged by chest radiograph findings.
- name: Cardiac Sarcoidosis
  description: Myocardial granulomas causing conduction abnormalities, heart failure, or sudden death.
- name: Neurosarcoidosis
  description: CNS involvement causing cranial neuropathies, meningitis, or mass lesions.
- name: Cutaneous Sarcoidosis
  description: Skin manifestations including erythema nodosum, lupus pernio, and papular lesions.
mechanistic_hypotheses:
- hypothesis_group_id: antigen_persistence_granuloma_chronicity_model
  hypothesis_label: Antigen Persistence / Th17.1 / mTORC1 Granuloma Chronicity Model
  status: EMERGING
  applies_to_subtypes:
  - Pulmonary Sarcoidosis
  description: >-
    Sarcoidosis is modeled as a genetically conditioned, antigen-driven
    granulomatous immune response in which poorly degradable or repeatedly
    encountered antigens are presented by macrophage-lineage antigen-presenting
    cells to CD4+ T cells. The activated T-cell compartment polarizes toward
    IFN-gamma-producing Th17.1/Th1-like effector states while regulatory T-cell
    restraint is insufficient. This cytokine circuit recruits and activates
    macrophages, promotes epithelioid and multinucleated giant-cell granuloma
    architecture, and intersects with macrophage-intrinsic metabolic programs
    such as mTORC1 activation. Resolution is hypothesized to require antigen
    clearance or sequestration plus restoration of regulatory and apoptotic
    checkpoints; chronic disease and fibrosis occur when antigen persistence,
    Th17.1 feedback, macrophage survival/proliferation, and tissue-repair
    programs remain engaged.
  notes: >-
    Retained as EMERGING after the 2026 OpenScientist hypothesis-search report (kb/hypotheses/Sarcoidosis/antigen_persistence_granuloma_chronicity_model/openscientist.md).
    The report judged the model partially supported: antigen-driven CD4 T-cell responses,
    Th17.1/Treg imbalance, and macrophage mTORC1 granuloma biology are individually
    well supported, but the integrated Th17.1-to-macrophage mTORC1 link remains unproven
    and fibrosis may diverge through distinct profibrotic/EMT-like tissue-remodeling
    programs. Best current fit is non-Lofgren, chronic/progressive pulmonary sarcoidosis
    rather than all sarcoidosis phenotypes. The cutaneous CLEAR trial is retained
    only as cross-organ discordance against the negative pulmonary trial; it does
    not extend the machine-readable hypothesis scope beyond Pulmonary Sarcoidosis.
    This model deliberately leaves the antigen source open; the competing vimentin_autoimmunity_model
    proposes a self-antigen rather than persistent microbial antigen as the disease-defining
    trigger, and the two are not mutually exclusive because molecular mimicry could
    unify them.
  evidence:
  - reference: PMID:38165044
    reference_title: "Immune mechanisms of granuloma formation in sarcoidosis and tuberculosis."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "Sarcoidosis is a complex immune-mediated disease characterized by clusters of immune cells called granulomas."
    explanation: >
      Recent mechanistic review used as the seed reference for the
      hypothesis-search deep-research run and for the antigen/T-cell/macrophage
      granuloma-chronicity framing.
  - reference: PMID:31273209
    reference_title: "Sarcoidosis."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "The disease develops in genetically predisposed individuals with exposure to an as-yet unknown antigen."
    explanation: >
      Nature Reviews Disease Primers review supports the central upstream
      premise of this hypothesis: genetically predisposed patients encounter an
      unknown antigenic trigger.
  - reference: PMID:23863960
    reference_title: "Oral antimycobacterial therapy in chronic cutaneous sarcoidosis: a randomized, single-masked, placebo-controlled study."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      For the primary end point of change in lesion size, as evidenced by a
      reduction in lesion diameter and number of granulomas, 7 of 10 patients
      randomized to the CLEAR regimen met this benchmark compared with 0 of 7
      randomized to placebo (P = .01, Fisher exact test).
    explanation: >-
      This small cutaneous-sarcoidosis trial supplies organ-specific clinical
      support for an antimicrobial-responsive process, but antibiotic
      immunomodulation, the small analyzed sample, and lack of organism
      identification prevent inference that viable mycobacteria maintain
      pulmonary granulomas.
  - reference: PMID:33387486
    reference_title: "Phase II Investigation of the Efficacy of Antimycobacterial Therapy in Chronic Pulmonary Sarcoidosis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Despite a significant decline in ESAT-6 immune responses, a 16-week CLEAR
      regimen provided no physiological benefit in FVC or 6MWD among patients
      with sarcoidosis.
    explanation: >-
      The multicenter placebo-controlled pulmonary trial weakens a
      viable, therapeutically eradicable mycobacterial-persistence account:
      immune reactivity fell without pulmonary physiological benefit. It does
      not exclude nonviable antigen remnants, other antigen classes, or a
      persistence mechanism confined to another organ or molecular subgroup.
- hypothesis_group_id: vimentin_autoimmunity_model
  hypothesis_label: Vimentin Autoantigen / HLA-DRB1*03 Autoimmunity Model
  status: EMERGING
  applies_to_subtypes:
  - Pulmonary Sarcoidosis
  description: >-
    An alternative to the persistent-microbial-antigen premise: in a subset of
    patients - most clearly the HLA-DRB1*03+ Lofgren phenotype - the
    disease-defining antigen is a self-protein rather than a foreign one, with
    the cytoskeletal protein vimentin as the leading candidate autoantigen.
    HLA-DRB1*03 presents vimentin-derived peptides to a strikingly restricted
    CD4+ T-cell receptor repertoire (Valpha2.3/Vbeta22), and linked T- and
    B-cell autoreactivity to vimentin is demonstrable in situ in the sarcoid
    lung. Under this model sarcoidosis (or at least its resolving
    HLA-restricted form) is better understood as an antigen-specific autoimmune
    disease. Rather than a strict self-versus-foreign dichotomy, the
    best-supported reading (2026 OpenScientist hypothesis-search report) is a
    multi-antigen milieu in the DR3+ sarcoid lung: HLA-DR molecules present
    several self-peptides, but only the vimentin response is demonstrably
    HLA-DRB1*03-restricted, whereas T-cell responses to ATP synthase and
    lysyl-tRNA synthetase also occur in DR3-negative patients, and the microbial
    antigen mycobacterial catalase-peroxidase (mKatG) is an independently
    documented tissue antigen whose relationship to the Valpha2.3/Vbeta22
    repertoire has not been directly tested. Vimentin is thus one prominent
    antigen among several rather than the unique disease initiator. The
    downstream CD4+ T-cell activation and Th17.1 effector chain is shared with
    the antigen-persistence model, and a direct molecular-mimicry bridge between
    vimentin and mycobacterial proteins remains speculative and is not supported
    at the linear-sequence level.
  notes: >-
    Held at EMERGING: the vimentin-autoantigen and HLA-DRB1*03/Valpha2.3-Vbeta22
    associations are well documented for pulmonary/Lofgren sarcoidosis, but
    vimentin is not proven to be the (or a) universal disease-initiating antigen,
    and the model is best supported in HLA-DRB1*03+ patients rather than across
    all sarcoidosis. Two caveats from the OpenScientist hypothesis-search report
    (kb/hypotheses/Sarcoidosis/vimentin_autoimmunity_model/openscientist.md;
    assessment sidecar under that directory's assessments/): (1) anti-vimentin
    autoreactivity is not sarcoidosis-specific (also in lupus nephritis and, as
    anti-citrullinated vimentin, rheumatoid arthritis), weakening its role as a
    disease-defining antigen; and (2) the resolution paradox - HLA-DRB1*03, the
    allele anchoring the model, is a dominant good-prognosis allele predicting
    spontaneous resolution, better fitting antigen recognition coupled to
    effective clearance than a self-perpetuating chronic autoimmune attack.
  evidence:
  - reference: PMID:30038611
    reference_title: "In Situ Humoral Immunity to Vimentin in HLA-DRB1*03(+) Patients With Pulmonary Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Vimentin has been implicated in pulmonary sarcoidosis as a T-cell autoantigen"
    explanation: >
      Directly establishes vimentin as an implicated T-cell autoantigen in
      pulmonary sarcoidosis in the HLA-DRB1*03 / restricted-TCR / Lofgren
      context, the central premise of this alternative hypothesis.
  - reference: PMID:30038611
    reference_title: "In Situ Humoral Immunity to Vimentin in HLA-DRB1*03(+) Patients With Pulmonary Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "linked in situ recognition of vimentin by both T- and B-cells in HLA-DRB1*03+ sarcoidosis patients"
    explanation: >
      Demonstrates coordinated T- and B-cell autoreactivity to vimentin within
      the HLA-DRB1*03+ sarcoid lung, supporting an antigen-specific autoimmune
      mechanism rather than a purely foreign-antigen response.
  - reference: PMID:26585430
    reference_title: "T-cell receptor-HLA-DRB1 associations suggest specific antigens in pulmonary sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Simultaneous expression of Vα2.3 with the Vβ22 chain was identified in the lungs of all HLA-DRB1*03(+) patients."
    explanation: Directly documents the restricted Vα2.3/Vβ22 CD4+ T-cell receptor repertoire in HLA-DRB1*03-positive pulmonary sarcoidosis.
  - reference: PMID:26585430
    reference_title: "T-cell receptor-HLA-DRB1 associations suggest specific antigens in pulmonary sarcoidosis."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "Molecular modelling revealed specific T-cell receptor-HLA-DRB1*03-peptide interactions, with a previously identified, sarcoidosis-associated vimentin peptide, (Vim)429-443 DSLPLVDTHSKRTLL, matching both the HLA peptide-binding cleft and distinct T-cell receptor features perfectly."
    explanation: Molecular modeling directly supports compatibility of the vimentin peptide with both the HLA-DRB1*03 binding cleft and the restricted TCR.
  - reference: PMID:35434591
    reference_title: "Systemic immune response to vimentin and granuloma formation in a model of pulmonary sarcoidosis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Vimentin-immunized mice developed lung granulomas following intravenous challenge with vimentin-coated beads."
    explanation: >
      Rare causal support: immunization against vimentin plus vimentin-bead
      challenge is sufficient to produce sarcoid-like Th1/Th17 lung granulomas in
      mice, moving vimentin from correlate toward trigger (model-organism; a bead
      model is not spontaneous human disease).
  - reference: PMID:19786367
    reference_title: "Autoimmune T cell responses to antigenic peptides presented by bronchoalveolar lavage cell HLA-DR molecules in sarcoidosis."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "there were strong T cell responses to a peptide derived from the cytoskeletal protein vimentin in 6 out of 11 DRB10301(pos) patients with active disease but not in patients with other HLA types"
    explanation: >
      Supports the HLA-DRB1*03-restricted vimentin T-cell response (present in
      DRB1*0301+ but not other-HLA patients), while the same study finds ATP
      synthase and lysyl-tRNA synthetase responses in DR3-negative patients too -
      so only the vimentin response is DR3-restricted, and vimentin is one of
      several DR-presented antigens rather than the unique trigger.
  - reference: PMID:15753209
    reference_title: "Mycobacterial catalase-peroxidase is a tissue antigen and target of the adaptive immune response in systemic sarcoidosis."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "suggesting that remnant mycobacterial catalase-peroxidase is one target of the adaptive immune response driving granulomatous inflammation in sarcoidosis"
    explanation: >
      Competing foreign-antigen evidence: mKatG is an independently documented
      sarcoid tissue antigen and adaptive-immune target (tissue proteomics plus
      anti-mKatG IgG; no TCR/HLA-restriction data), qualifying the
      self-antigen-only framing. Its relationship to the Valpha2.3/Vbeta22 public
      clone has not been directly tested, so it supports a multi-antigen milieu
      rather than a single DR3-restricted cross-reactive response.
  - reference: PMID:20187937
    reference_title: "Different HLA-DRB1 allele distributions in distinct clinical subgroups of sarcoidosis patients."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "the clinical influence of DRB1*03 (good prognosis) dominated over that of DRB1*15 (bad prognosis)"
    explanation: >
      The resolution paradox: HLA-DRB1*03, the allele anchoring this model,
      predicts good prognosis / spontaneous resolution, which is difficult to
      reconcile with a chronic self-perpetuating autoimmune mechanism.
- hypothesis_group_id: environmental_exposure_host_susceptibility_trigger_model
  hypothesis_label: Environmental Exposure × Host Susceptibility Trigger Model
  status: EMERGING
  applies_to_subtypes:
  - Pulmonary Sarcoidosis
  description: >-
    Specific inhaled bioaerosols and inorganic particles are associated with
    pulmonary-sarcoidosis risk. The hypothesis is that, in a subset of
    susceptible hosts, a particular exposure initiates disease through an
    exposure-specific innate-sensing or antigen-presentation program that
    changes CD4+ T-cell polarization. HLA and other immune-risk alleles may
    modify that response and the resulting phenotype. This upstream model
    complements the antigen-persistence/granuloma-chronicity model; it does not
    assert that distinct exposure classes share one receptor or pathway. The
    exposure-to-sensor/presentation bridge and exposure-by-genotype
    combinations remain unproven.
  notes: >-
    Retained as EMERGING after the 2026 disease-level and focused
    OpenScientist reports
    (research/Sarcoidosis-deep-research-openscientist.md and
    kb/hypotheses/Sarcoidosis/environmental_exposure_host_susceptibility_trigger_model/openscientist.md).
    Human data support modest exposure associations and host-genetic main
    effects. Direct ACCESS HLA-by-exposure signals remain exploratory and
    unreplicated; separate single-cohort genome-wide analyses report
    smoking-by-locus and insecticide-by-locus interactions, but do not replicate
    the ACCESS pairs. A WTC study found no interaction with its exposure-degree
    measure, and no exposure-specific sensor-to-CD4 mechanism has been shown in
    idiopathic sarcoidosis. Beryllium-associated granulomatous disease is a
    separate exposure-defined differential diagnosis, not evidence that its
    HLA-restricted mechanism operates in idiopathic pulmonary sarcoidosis. No
    exposure-specific causal edge is curated.
  evidence:
  - reference: PMID:15347561
    reference_title: "A case control etiologic study of sarcoidosis: environmental and occupational risk factors."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In multivariable modeling, we observed elevated ORs for work in areas with
      musty odors (OR 1.62, CI 1.24-2.11) and with occupational exposure to
      insecticides (OR 1.61, CI 1.13-2.28), and a decreased OR related to ever
      smoking cigarettes (OR 0.65, CI 0.51-0.82).
    explanation: >-
      The matched ACCESS case-control study supports modest, exposure-class
      associations, not a specific initiating antigen, receptor, or causal
      pathway; questionnaire exposure ascertainment and residual confounding
      remain limitations.
  - reference: PMID:19382531
    reference_title: HLA and environmental interactions in sarcoidosis.
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Significant interaction was observed between HLA DRB1*1101 and
      insecticide exposure at work (p < 0.10) and suggestive interaction was
      observed between HLA DRB1*1101 and exposure to mold and musty odors and
      DRB1*1501 and insecticide exposure at work (P < 0.15).
    explanation: >-
      The ACCESS case-control analysis provides exposure-by-HLA leads, but its
      exploratory significance thresholds and phenotype stratification require
      independent replication before these pairs are modeled as causal.
  - reference: PMID:31819081
    reference_title: A Gene-Environment Interaction Between Smoking and Gene polymorphisms Provides a High Risk of Two Subgroups of Sarcoidosis.
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Assessment of smoking effects with inclusion of genetic information
      revealed 53 (in LS) and 34 (in non-LS) SNP-smoking additive interactions
      at false discovery rate (FDR) below 5%. The lead signals interacting with
      smoking were rs12132140 (AP = 0.56, 95% CI = 0.22-0.90), p = 1.28e-03) in
      FCRL1 for LS and rs61780312 (AP = 0.62, 95% CI = 0.28-0.90), p = 3e-04) in
      IL23R for non-LS.
    explanation: >-
      This Swedish case-control study supports subgroup-specific,
      genotype-dependent smoking interactions in one cohort. It does not
      replicate the ACCESS HLA-exposure pairs, identify an initiating antigen
      or sensor, or establish a causal smoking effect; independent and
      functional replication remain necessary.
  - reference: PMID:30793815
    reference_title: Extended methods for gene-environment-wide interaction scans in studies of admixed individuals with varying degrees of relationships.
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We applied the proposed method to conduct a GEWIS of a known sarcoidosis
      risk factor (insecticide exposure) and risk of sarcoidosis in African
      Americans and identified two novel loci with suggestive evidence of G × E
      interaction.
    explanation: >-
      The African American GEWIS supplies a broader insecticide-by-locus lead,
      but the evidence was explicitly suggestive and does not replicate the
      specific ACCESS HLA-exposure pairs or define an exposure-to-immune
      mechanism.
  - reference: PMID:32941653
    reference_title: Simultaneous testing of immunological sensitization to multiple antigens in sarcoidosis reveals an association with inorganic antigens specifically related to a fibrotic phenotype.
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A significantly higher percentage of sarcoidosis patients (27·6%) than
      controls (4·2%) had an immunological response to metals or silica
      (P = 0·014). A higher percentage of these sarcoidosis patients showed
      fibrosis on chest X-ray 5 years after the diagnosis (69·2 versus 30·3%,
      P = 0·016).
    explanation: >-
      In the tested inorganic-antigen subset (105 patients and 24 controls),
      ELISPOT sensitization was associated with later radiographic fibrosis and
      therefore supplies a phenotype-stratification lead. Sensitization is not
      verified exposure, a genotype interaction, proof of disease initiation,
      or causal evidence.
pathophysiology:
- name: Genetic Susceptibility
  description: >
    Sarcoidosis is a polygenic immune disorder. Risk-associated variants in HLA
    class II (DRB1 lineages), the truncating splice variant rs2076530 in BTNL2
    (a T-cell co-inhibitory butyrophilin-like immunoglobulin superfamily member),
    the missense ANXA11 R230C (rs1049550), NOTCH4, and IL27RA collectively shift
    antigen presentation, T-cell co-stimulation/inhibition, and macrophage
    apoptosis thresholds, predisposing to exaggerated granulomatous response on
    antigen encounter.
  evidence:
  - reference: PMID:15735647
    reference_title: "Sarcoidosis is associated with a truncating splice site mutation in BTNL2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The G --> A transition constituting rs2076530 leads to the use of a cryptic splice site located 4 bp upstream of the affected wild-type donor site. Transcripts of the risk-associated allele have a premature stop in the spliced mRNA. The resulting protein lacks the C-terminal IgC domain and transmembrane helix, thereby disrupting the membrane localization of the protein"
    explanation: This case-control SNP scan identifies the truncating BTNL2 splice variant rs2076530 as a sarcoidosis risk factor independent of HLA-DRB1, with a defined molecular consequence (loss of membrane-anchored co-inhibitory protein).
  - reference: PMID:19165924
    reference_title: "Genome-wide association study identifies ANXA11 as a new susceptibility locus for sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The strongest association signal maps to the ANXA11 (annexin A11) gene on chromosome 10q22.3."
    explanation: GWAS plus replication establishes ANXA11 as a major sarcoidosis susceptibility locus; the lead missense R230C (rs1049550) variant defined in this work is the molecular entry point for the apoptosis/proliferation arm of the pathograph.
  - reference: PMID:19165924
    reference_title: "Genome-wide association study identifies ANXA11 as a new susceptibility locus for sarcoidosis."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "Annexin A11 has complex and essential functions in several biological pathways, including apoptosis and proliferation."
    explanation: Functional context for why ANXA11 risk variants are mechanistically relevant - the gene regulates apoptosis and proliferation, which are precisely the macrophage processes dysregulated in granuloma maintenance.
  cell_types:
  - preferred_term: CD4-positive helper T cell
    term:
      id: CL:0000492
      label: CD4-positive helper T cell
  biological_processes:
  - preferred_term: antigen processing and presentation
    term:
      id: GO:0019882
      label: antigen processing and presentation
  downstream:
  - target: Antigen Recognition and CD4+ T-Cell Activation
    description: Risk alleles in HLA-DRB1 and BTNL2 alter MHC class II antigen presentation and T-cell co-inhibition, lowering the threshold for an exaggerated CD4+ T-cell response to a triggering antigen.
    causal_link_type: DIRECT
    hypothesis_groups:
    - antigen_persistence_granuloma_chronicity_model
    - vimentin_autoimmunity_model
  - target: Self-Antigen Vimentin Presentation by HLA-DRB1*03
    description: In the vimentin autoimmunity model specifically, the HLA-DRB1*03 risk allele presents the self-peptide vimentin (Vim)429-443 to the restricted Valpha2.3/Vbeta22 CD4+ T-cell repertoire - the model-distinguishing self-antigen presentation step.
    causal_link_type: DIRECT
    hypothesis_groups:
    - vimentin_autoimmunity_model
- name: Self-Antigen Vimentin Presentation by HLA-DRB1*03
  biological_scale: MOLECULAR
  description: >
    Vimentin-specific arm of antigen presentation (the step that distinguishes
    the vimentin autoimmunity model from the persistent-microbial-antigen model):
    HLA-DRB1*03 presents the self-peptide vimentin (Vim)429-443
    (DSLPLVDTHSKRTLL) to a public, clonally restricted Valpha2.3/Vbeta22 CD4+
    T-cell receptor repertoire found in the lungs of essentially all
    HLA-DRB1*03+ patients, with molecular modelling supporting a precise fit of
    the peptide to both the HLA cleft and the restricted TCR.
  evidence:
  - reference: PMID:26585430
    reference_title: "T-cell receptor-HLA-DRB1 associations suggest specific antigens in pulmonary sarcoidosis."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "Molecular modelling revealed specific T-cell receptor-HLA-DRB1*03-peptide interactions, with a previously identified, sarcoidosis-associated vimentin peptide, (Vim)429-443 DSLPLVDTHSKRTLL, matching both the HLA peptide-binding cleft and distinct T-cell receptor features perfectly."
    explanation: Molecular modelling supports HLA-DRB1*03 presentation of the vimentin Vim429-443 peptide to the restricted TCR, the self-antigen presentation step unique to this model.
  - reference: PMID:26585430
    reference_title: "T-cell receptor-HLA-DRB1 associations suggest specific antigens in pulmonary sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Simultaneous expression of Vα2.3 with the Vβ22 chain was identified in the lungs of all HLA-DRB1*03(+) patients."
    explanation: Documents the restricted Valpha2.3/Vbeta22 CD4+ T-cell repertoire in the lungs of HLA-DRB1*03+ patients that recognizes the presented vimentin peptide.
  - reference: PMID:17975675
    reference_title: "Identification of HLA-DR-bound peptides presented by human bronchoalveolar lavage cells in sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified 78 amino acid sequences from self proteins presented in the lungs of sarcoidosis patients, some of which were well-known autoantigens such as vimentin and ATP synthase."
    explanation: Direct physical-presentation evidence - acid-eluted HLA-DR peptides from DRB1*0301+ patient BAL cells include vimentin, substantiating the presentation step beyond molecular modelling (and consistent with the multi-antigen milieu, since ATP synthase is co-presented).
  cell_types:
  - preferred_term: alveolar macrophage
    term:
      id: CL:0000583
      label: alveolar macrophage
  - preferred_term: CD4-positive helper T cell
    term:
      id: CL:0000492
      label: CD4-positive helper T cell
  biological_processes:
  - preferred_term: antigen processing and presentation of peptide antigen via MHC class II
    term:
      id: GO:0002495
      label: antigen processing and presentation of peptide antigen via MHC class II
  downstream:
  - target: Antigen Recognition and CD4+ T-Cell Activation
    description: HLA-DRB1*03-presented vimentin peptide is recognized by the restricted Valpha2.3/Vbeta22 CD4+ T cells, feeding the shared antigen-recognition and Th17.1 effector chain.
    causal_link_type: DIRECT
    hypothesis_groups:
    - vimentin_autoimmunity_model
- name: Antigen Recognition and CD4+ T-Cell Activation
  description: >
    Susceptibility alleles permit MHC class II presentation of candidate
    microbial or self peptides to CD4+ T cells, which expand clonally and may
    acquire a Th1/Th17.1 effector program with high IFN-gamma production.
    Bioaerosols or inorganic particles could instead supply antigenic material,
    generate modified-self epitopes, or act through innate or adjuvant
    pathways, but their route to HLA-restricted T-cell activation remains
    unresolved.
  evidence:
  - reference: PMID:21092305
    reference_title: "Multiple mycobacterial antigens are targets of the adaptive immune response in pulmonary sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Alveolar T-cells from twenty-two of the 31 sarcoidosis patients produced a CD4+ response to at least one of ESAT-6, katG, Ag85A, sodA, or HSP, compared to two of 14 PPD- controls (p = 0.0008)"
    explanation: Direct demonstration that lung-resident T cells from sarcoidosis patients recognize mycobacterial antigens, supporting an antigen-driven step linking the susceptibility node to T-cell activation.
  - reference: PMID:31273209
    reference_title: "Sarcoidosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The typical T cell accumulation, local T cell immune response and granuloma formation in the lungs indicate that the inflammatory response in sarcoidosis is induced by specific antigens, possibly including self-antigens, which is consistent with an autoimmune involvement."
    explanation: >
      Review-level synthesis supports antigen-driven local T-cell responses in
      pulmonary sarcoidosis while preserving uncertainty about antigen identity.
  cell_types:
  - preferred_term: CD4-positive helper T cell
    term:
      id: CL:0000492
      label: CD4-positive helper T cell
  - preferred_term: alveolar macrophage
    term:
      id: CL:0000583
      label: alveolar macrophage
  biological_processes:
  - preferred_term: antigen processing and presentation of peptide antigen via MHC class II
    term:
      id: GO:0002495
      label: antigen processing and presentation of peptide antigen via MHC class II
  - preferred_term: T cell activation
    term:
      id: GO:0042110
      label: T cell activation
  downstream:
  - target: Th17.1 Polarization and IFN-gamma Production
    description: Antigen-activated CD4+ T cells in lung tissue polarize toward an IFN-gamma-producing Th17.1 phenotype that drives sustained granulomatous inflammation.
    causal_link_type: DIRECT
    hypothesis_groups:
    - antigen_persistence_granuloma_chronicity_model
    - vimentin_autoimmunity_model
- name: Th17.1 Polarization and IFN-gamma Production
  description: >
    Plasticity within the Th17 lineage produces IFN-gamma-producing Th17.1 cells
    that are the dominant source of IFN-gamma in pulmonary sarcoidosis and
    correlate with progressive (non-Lofgren) disease. Concurrent Treg dysfunction
    (impaired survival, altered CTLA-4 expression) removes the brake on this
    effector response.
  evidence:
  - reference: PMID:27379969
    reference_title: "T-cell immunology in sarcoidosis: Disruption of a delicate balance between helper and regulatory T-cells."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "it was demonstrated that Th17.1-cells rather than Th1-cells are responsible for the exaggerated IFN-γ production in pulmonary sarcoidosis."
    explanation: Reviews the paradigm shift identifying Th17.1 cells (not classical Th1) as the dominant IFN-gamma source in sarcoidosis, anchoring this node mechanistically.
  - reference: PMID:29310925
    reference_title: "Th17-lineage cells in pulmonary sarcoidosis and Lofgren's syndrome: Friend or foe?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In non-LS sarcoidosis patients, IFN-γ-producing Th17.1-cells appear to be more pathogenic and possibly linked to disease progression"
    explanation: Direct support that Th17.1 polarization marks the pathogenic, progression-prone arm of sarcoidosis and is the upstream effector that drives macrophage transformation.
  - reference: PMID:24882950
    reference_title: "Bronchoalveolar lavage fluid IFN-gamma+ Th17 cells and regulatory T cells in pulmonary sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The proportion of Th17 cells positive for IFN-gamma was greater in sarcoidosis than controls (median 72.4% versus 31%, P = 0.0005) and increased with radiologic stage (N = 23, rho = 0.45, and P = 0.03)."
    explanation: Quantitative evidence that the IFN-gamma+ Th17 (Th17.1) compartment is enriched in lung lavage of sarcoidosis patients and tracks with radiographic stage.
  - reference: PMID:26376720
    reference_title: "Impaired survival of regulatory T cells in pulmonary sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In untreated patients with active pulmonary sarcoidosis, Tregs show impaired survival and enhanced apoptotic susceptibility towards CD95L. Increased apoptosis likely contributes to the insufficient immunosuppressive function of sarcoidosis Tregs."
    explanation: Treg apoptotic susceptibility removes the suppressive brake on Th17.1 effector cells, helping maintain chronic granulomatous inflammation.
  cell_types:
  - preferred_term: T-helper 17 cell
    term:
      id: CL:0000899
      label: T-helper 17 cell
  - preferred_term: regulatory T cell
    term:
      id: CL:0000815
      label: regulatory T cell
  biological_processes:
  - preferred_term: T-helper 17 type immune response
    term:
      id: GO:0072538
      label: T-helper 17 type immune response
  - preferred_term: regulatory T cell apoptotic process
    term:
      id: GO:1902482
      label: regulatory T cell apoptotic process
  downstream:
  - target: Macrophage Activation and mTORC1 Hyperactivation
    description: IFN-gamma-rich Th17.1 inflammation, persistent antigen, and other tissue signals are hypothesized to converge on recruitment, activation, and metabolic reprogramming of macrophages; direct Th17.1-to-macrophage mTORC1 causality in human sarcoidosis remains unproven.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Unresolved coupling between Th17.1 cytokines, persistent antigen, macrophage growth/survival signals, and macrophage mTORC1 activation.
    hypothesis_groups:
    - antigen_persistence_granuloma_chronicity_model
- name: Macrophage Activation and mTORC1 Hyperactivation
  description: >
    Chronic antigenic stimulation drives macrophage hypertrophy, proliferation,
    and transformation into epithelioid cells. A macrophage-intrinsic increase
    in mTORC1 signaling (genetically modeled by Tsc2 deletion) is sufficient to
    initiate and sustain non-caseating granulomas, via CDK4-dependent proliferation,
    glycolytic reprogramming, and suppression of macrophage apoptosis. mTORC1
    activation is enriched in progressive human sarcoidosis lesions.
  evidence:
  - reference: PMID:28092373
    reference_title: "Chronic signaling via the metabolic checkpoint kinase mTORC1 induces macrophage granuloma formation and marks sarcoidosis progression."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We found that activation of the metabolic checkpoint kinase mTORC1 in macrophages by deletion of the gene encoding tuberous sclerosis 2 (Tsc2) was sufficient to induce hypertrophy and proliferation, resulting in excessive granuloma formation in vivo."
    explanation: Conditional Tsc2 deletion in mouse myeloid cells is sufficient to recapitulate sarcoid-like granulomas, mechanistically anchoring macrophage-intrinsic mTORC1 hyperactivation as a granuloma-initiating step.
  - reference: PMID:28092373
    reference_title: "Chronic signaling via the metabolic checkpoint kinase mTORC1 induces macrophage granuloma formation and marks sarcoidosis progression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In human sarcoidosis patients, mTORC1 activation, macrophage proliferation and glycolysis were identified as hallmarks that correlated with clinical disease progression."
    explanation: Re-analysis of human sarcoidosis biopsies translates the mouse mechanism - mTORC1 activity, macrophage proliferation, and glycolysis distinguish progressive from self-limiting disease in patients.
  - reference: PMID:29104468
    reference_title: "Extensively disturbance of regulatory T cells - Th17 cells balance in stage II pulmonary sarcoidosis."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "Disturbance of T memory cells, Th1/Th2, and Tregs/Th17 cells, and activation of PI3K/Akt signaling were seen in newly diagnosed stage II pulmonary sarcoidosis"
    explanation: Independent confirmation that PI3K/Akt (upstream of mTORC1) is activated in pulmonary sarcoidosis BAL cells, supporting parallel relevance of this metabolic axis in human disease.
  - reference: PMID:38038136
    reference_title: "Activation of the pentose phosphate pathway in macrophages is crucial for granuloma formation in sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Macrophages in the sarcoidosis lesion were hypermetabolic, especially in the pentose phosphate pathway (PPP)."
    explanation: >
      Single-cell RNA-seq of sarcoidosis lesions shows granuloma macrophages
      are hypermetabolic with pentose phosphate pathway (PPP) activation,
      extending the macrophage metabolic-reprogramming arm beyond glycolysis;
      PPP inhibitors attenuated giant-cell and murine granuloma formation,
      identifying the PPP as a candidate steroid-sparing target.
  cell_types:
  - preferred_term: epithelioid macrophage
    term:
      id: CL:0002150
      label: epithelioid macrophage
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  biological_processes:
  - preferred_term: TORC1 signaling
    term:
      id: GO:0038202
      label: TORC1 signaling
    modifier: INCREASED
  - preferred_term: macrophage activation
    term:
      id: GO:0042116
      label: macrophage activation
  - preferred_term: glycolytic process
    term:
      id: GO:0006096
      label: glycolytic process
    modifier: INCREASED
  - preferred_term: pentose-phosphate shunt
    term:
      id: GO:0006098
      label: pentose-phosphate shunt
    modifier: INCREASED
  - preferred_term: negative regulation of macrophage apoptotic process
    term:
      id: GO:2000110
      label: negative regulation of macrophage apoptotic process
  downstream:
  - target: Granuloma Formation
    description: mTORC1-driven hypertrophic, proliferating macrophages aggregate with multinucleated giant cells and CD4+ T cells to form non-caseating granulomas.
    causal_link_type: DIRECT
    hypothesis_groups:
    - antigen_persistence_granuloma_chronicity_model
- name: Granuloma Formation
  description: >
    Non-caseating granulomas consist of organized collections of activated
    macrophages (epithelioid cells), multinucleated giant cells, and CD4+ T cells.
    Th1/Th17.1 immune responses drive granuloma development in response to
    persistent antigens. Granulomas are the defining histopathologic lesion that
    mediates the downstream organ-level phenotypes of sarcoidosis. This node
    conforms to the conserved granuloma-formation module: sarcoid granulomas are
    characteristically non-caseating, distinguishing them from the caseating
    granulomas of tuberculosis.
  conforms_to: "granuloma_formation#Epithelioid Transformation and Multinucleated Giant Cell Formation"
  evidence:
  - reference: PMID:35011621
    reference_title: "Clinical Features, Histopathology and Differential Diagnosis of Sarcoidosis."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "Sarcoidosis is a chameleon disease of unknown etiology, characterized by the growth of non-necrotizing and non-caseating granulomas"
    explanation: "This review confirms the characteristic non-caseating granuloma formation in sarcoidosis."
  - reference: PMID:38165044
    reference_title: "Immune mechanisms of granuloma formation in sarcoidosis and tuberculosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Sarcoidosis is a complex immune-mediated disease characterized by clusters of immune cells called granulomas."
    explanation: This 2024 JCI mechanistic review frames sarcoidosis as a granuloma-defined immune-mediated disease and is the source for the integrated antigen-T-cell-macrophage causal chain summarized here.
  - reference: PMID:33329511
    reference_title: "Treatment of Sarcoidosis: A Multidisciplinary Approach."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The sarcoidosis granuloma is formed by a distinct conglomeration of multinucleated giant cells and epithelioid macrophages surrounded by a rim of CD4+ T cells"
    explanation: >
      Full-text review-level support for the core immune-cell architecture of
      sarcoid granulomas: macrophage-lineage giant/epithelioid cells surrounded
      by CD4+ T cells.
  cell_types:
  - preferred_term: epithelioid macrophage
    term:
      id: CL:0002150
      label: epithelioid macrophage
  - preferred_term: multinucleated giant cell
    term:
      id: CL:0000647
      label: multinucleated giant cell
  - preferred_term: CD4-positive helper T cell
    term:
      id: CL:0000492
      label: CD4-positive helper T cell
  biological_processes:
  - preferred_term: granuloma formation
    term:
      id: GO:0002432
      label: granuloma formation
  - preferred_term: Macrophage fusion into multinucleated giant cells
    term:
      id: GO:0000768
      label: syncytium formation by cell-cell fusion
    modifier: INCREASED
  downstream:
  - target: Macrophage Calcitriol Production
    description: Granuloma macrophages express CYP27B1 and convert 25-hydroxyvitamin D to active 1,25-dihydroxyvitamin D outside normal renal regulation, predisposing to hypercalcemia.
    causal_link_type: DIRECT
  - target: Macrophage ACE Production
    description: Epithelioid macrophages within granulomas synthesize angiotensin-converting enzyme, producing the elevated serum ACE characteristic of active sarcoidosis.
    causal_link_type: DIRECT
  - target: Fibrotic Tissue Remodeling
    description: Persistent granulomatous inflammation is associated with later TGF-beta-driven myofibroblast programs and excessive ECM deposition in a subset of patients, but the switch from active granulomas to fibrotic remodeling is not resolved and may involve partly distinct profibrotic pathways.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Unresolved granuloma-to-fibrosis switch involving TGF-beta signaling, epithelial-mesenchymal transition-like programs, fibroblast activation, and chronic tissue injury.
    hypothesis_groups:
    - antigen_persistence_granuloma_chronicity_model
- name: Macrophage Calcitriol Production
  description: >
    Activated monocytes and macrophages within sarcoid granulomas express
    1-alpha-hydroxylase (CYP27B1), converting 25-hydroxyvitamin D to
    1,25-dihydroxyvitamin D outside normal PTH/FGF23 regulation. This extrarenal
    calcitriol synthesis, with optional PTHrP secretion, drives intestinal calcium
    absorption and bone resorption, producing hypercalcemia and hypercalciuria.
  evidence:
  - reference: PMID:24663253
    reference_title: "Serum vitamin D levels may not reflect tissue-level vitamin D in sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypercalcemia in sarcoidosis is due to three mechanistic reasons: (1) systemic conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by the enzyme 1-alpha hydroxylase produced by activated monocyte/macrophage system, (2) production of parathormone-related peptide (PTHrP) by the sarcoid granuloma, (3) tissue-level conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by 1-alphahydroxylase produced by local monocyte/macrophage system in the sarcoid granuloma."
    explanation: Mechanistic case-based report explicitly attributing sarcoid hypercalcemia to macrophage-driven extrarenal CYP27B1 expression and PTHrP, defining the molecular bridge from granuloma to the hypercalcemia phenotype.
  - reference: PMID:23337133
    reference_title: "Hypercalcemia associated with mineral oil-induced sclerosing paraffinomas."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypercalcemia associated with mineral oil induced skin lesions is likely driven by unregulated expression of CYP27b1 by inflammatory monocytes and macrophages infiltrating the dermis."
    explanation: A non-sarcoidosis granulomatous condition independently demonstrates that ectopic CYP27B1 expression in tissue macrophages causes hypercalcemia, generalizing the macrophage-calcitriol mechanism.
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  biological_processes:
  - preferred_term: vitamin D metabolic process
    term:
      id: GO:0042359
      label: vitamin D metabolic process
    modifier: INCREASED
  downstream:
  - target: Hypercalcemia
    description: Extrarenal 1,25-dihydroxyvitamin D production by granuloma macrophages causes hypercalcemia in approximately 5-10% of patients.
    causal_link_type: DIRECT
- name: Macrophage ACE Production
  description: >
    Epithelioid macrophages within granulomas constitutively express
    angiotensin-converting enzyme (ACE), and serum ACE elevation reflects total
    granuloma burden. Single-cell RNA-seq of cutaneous sarcoid granulomas has
    identified TREM2-positive ACE-expressing macrophages as a granuloma-resident
    population, supporting macrophage origin of the serum biomarker.
  evidence:
  - reference: PMID:38038136
    reference_title: "Activation of the pentose phosphate pathway in macrophages is crucial for granuloma formation in sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the percentages of triggering receptor expressed on myeloid cells 2-positive (TREM2-positive) macrophages expressing angiotensin-converting enzyme (ACE) and lysozyme, diagnostic makers of sarcoidosis, were increased in cutaneous sarcoidosis granulomas."
    explanation: Single-cell RNA-seq demonstrates TREM2+ macrophages expressing ACE are enriched in sarcoid granulomas, directly supporting the macrophage origin of serum ACE elevation.
  cell_types:
  - preferred_term: epithelioid macrophage
    term:
      id: CL:0002150
      label: epithelioid macrophage
  downstream:
  - target: Elevated ACE
    description: Granuloma-resident epithelioid macrophages secrete ACE; circulating levels are raised in active sarcoidosis and broadly correlate with granuloma burden.
    causal_link_type: DIRECT
- name: Fibrotic Tissue Remodeling
  description: >
    In approximately 10-30% of patients with chronic disease, persistent
    granulomatous inflammation transitions to a profibrotic state characterized
    by TGF-beta signaling, fibroblast/myofibroblast activation, and excessive
    extracellular matrix deposition. The end result is irreversible parenchymal
    fibrosis with restrictive physiology, fibrocystic remodeling, and respiratory
    failure. This node conforms to the conserved fibrotic response module.
  conforms_to: "fibrotic_response#Mesenchymal Cell Activation"
  evidence:
  - reference: PMID:41095908
    reference_title: "Immunosuppressive Therapies in Pulmonary Sarcoidosis: A Practical, Evidence-Based Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although many patients experience spontaneous remission, approximately 10-30% develop progressive pulmonary disease, which may lead to fibrocystic changes, respiratory failure, and death."
    explanation: This review directly supports progression from pulmonary sarcoidosis to fibrocystic and fibrotic lung disease in a substantial subset of patients.
  cell_types:
  - preferred_term: fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  biological_processes:
  - preferred_term: extracellular matrix organization
    term:
      id: GO:0030198
      label: extracellular matrix organization
    modifier: INCREASED
  downstream:
  - target: Pulmonary Fibrosis
    description: Persistent granulomatous inflammation drives ECM deposition, restrictive physiology, and irreversible fibrocystic remodeling in 10-30% of patients.
    causal_link_type: DIRECT
phenotypes:
- name: Mediastinal Lymphadenopathy
  category: Pulmonary
  frequency: VERY_FREQUENT
  description: Symmetric enlargement of hilar and mediastinal lymph nodes, often the presenting finding on chest radiograph.
  phenotype_term:
    preferred_term: Mediastinal lymphadenopathy
    term:
      id: HP:0100721
      label: Mediastinal lymphadenopathy
  evidence:
  - reference: PMID:31485575
    reference_title: "Clinical Manifestations, Diagnosis, and Treatment of Sarcoidosis."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "Although intrathoracic involvement is the hallmark of the disease, present in over 90% of patients, sarcoidosis can affect virtually any organ."
    explanation: This Mayo Clinic review strongly supports intrathoracic involvement as the dominant manifestation of sarcoidosis, but only indirectly supports mediastinal lymphadenopathy specifically.
- name: Dyspnea
  category: Pulmonary
  frequency: FREQUENT
  description: Shortness of breath due to pulmonary involvement and reduced lung function.
  phenotype_term:
    preferred_term: Dyspnea
    term:
      id: HP:0002094
      label: Dyspnea
  evidence:
  - reference: PMID:38227868
    reference_title: "Sarcoidosis: Evaluation and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ongoing dyspnea and dry cough in a young to middle-aged adult should increase the suspicion for sarcoidosis."
    explanation: This 2024 American Family Physician review identifies dyspnea as a key presenting symptom that should raise suspicion for sarcoidosis.
- name: Nonproductive Cough
  category: Pulmonary
  frequency: FREQUENT
  description: Dry, non-productive cough from airway and parenchymal inflammation.
  phenotype_term:
    preferred_term: Nonproductive cough
    term:
      id: HP:0031246
      label: Nonproductive cough
  evidence:
  - reference: PMID:38227868
    reference_title: "Sarcoidosis: Evaluation and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ongoing dyspnea and dry cough in a young to middle-aged adult should increase the suspicion for sarcoidosis."
    explanation: Dry cough is identified as a hallmark symptom that should raise clinical suspicion for sarcoidosis in younger adults.
- name: Fatigue
  category: Constitutional
  frequency: FREQUENT
  description: Chronic fatigue is one of the most debilitating symptoms, often persisting after disease resolution.
  phenotype_term:
    preferred_term: Fatigue
    term:
      id: HP:0012378
      label: Fatigue
  evidence:
  - reference: PMID:38227868
    reference_title: "Sarcoidosis: Evaluation and Treatment."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with sarcoidosis can exhibit constitutional symptoms such as fever, unintentional weight loss, and fatigue."
    explanation: This review supports fatigue as a recognized constitutional symptom in sarcoidosis, but the wording is not strong enough on its own to justify a VERY_FREQUENT frequency assignment.
- name: Erythema Nodosum
  category: Dermatologic
  frequency: OCCASIONAL
  description: Painful red nodules on the shins, often associated with acute sarcoidosis (Lofgren syndrome).
  phenotype_term:
    preferred_term: Erythema nodosum
    term:
      id: HP:0012219
      label: Erythema nodosum
  evidence:
  - reference: PMID:39082153
    reference_title: "Löfgren syndrome, characteristics of Japanese cases: A case and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Löfgren syndrome (LS) is a sarcoidosis subtype characterised by an acute disease course, bilateral hilar lymphadenopathy (BHL), erythema nodosum (EN), and ankle arthritis."
    explanation: This review of Lofgren syndrome directly supports erythema nodosum as a recognized acute cutaneous manifestation of sarcoidosis.
- name: Uveitis
  category: Ophthalmologic
  frequency: OCCASIONAL
  description: Eye inflammation that can lead to vision impairment if untreated. May be anterior, posterior, or panuveitis.
  phenotype_term:
    preferred_term: Uveitis
    term:
      id: HP:0000554
      label: Uveitis
  evidence:
  - reference: PMID:33173272
    reference_title: "Ocular Manifestations of Sarcoidosis in a South Florida Population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Uveitis was the most common ocular manifestation."
    explanation: This retrospective series directly supports uveitis as a common ocular manifestation among patients with ocular sarcoidosis.
- name: Hypercalcemia
  category: Metabolic
  frequency: OCCASIONAL
  description: Elevated serum calcium driven by extrarenal 1,25-dihydroxyvitamin D synthesis by granuloma macrophages, with optional PTHrP secretion. Affects approximately 5-10% of patients and may cause nephrolithiasis or nephrocalcinosis.
  phenotype_term:
    preferred_term: Hypercalcemia
    term:
      id: HP:0003072
      label: Hypercalcemia
  evidence:
  - reference: PMID:24663253
    reference_title: "Serum vitamin D levels may not reflect tissue-level vitamin D in sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypercalcemia in sarcoidosis is due to three mechanistic reasons: (1) systemic conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by the enzyme 1-alpha hydroxylase produced by activated monocyte/macrophage system, (2) production of parathormone-related peptide (PTHrP) by the sarcoid granuloma, (3) tissue-level conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by 1-alphahydroxylase produced by local monocyte/macrophage system in the sarcoid granuloma."
    explanation: Directly supports hypercalcemia as a phenotype of sarcoidosis with a defined macrophage-CYP27B1 mechanism.
- name: Pulmonary Fibrosis
  category: Pulmonary
  frequency: OCCASIONAL
  description: Irreversible parenchymal fibrosis in approximately 10-30% of patients with chronic disease, producing restrictive lung physiology, fibrocystic remodeling, and respiratory failure.
  subtype: Pulmonary Sarcoidosis
  phenotype_term:
    preferred_term: Pulmonary fibrosis
    term:
      id: HP:0002206
      label: Pulmonary fibrosis
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:41095908
    reference_title: "Immunosuppressive Therapies in Pulmonary Sarcoidosis: A Practical, Evidence-Based Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although many patients experience spontaneous remission, approximately 10-30% develop progressive pulmonary disease, which may lead to fibrocystic changes, respiratory failure, and death."
    explanation: Directly supports pulmonary fibrosis as a progression-related phenotype occurring in a substantial subset of sarcoidosis patients.
- name: Atrioventricular Block
  category: Cardiac
  frequency: OCCASIONAL
  description: Conduction system involvement from myocardial granulomas. AV block (often high-grade) is a common cardiac sarcoidosis presentation; QRS prolongation greater than 120 ms is a screening indicator.
  subtype: Cardiac Sarcoidosis
  phenotype_term:
    preferred_term: Atrioventricular block
    term:
      id: HP:0001678
      label: Atrioventricular block
  evidence:
  - reference: PMID:39621157
    reference_title: "Holter Monitoring and Cardiac Biomarkers in Screening for Cardiac Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "male gender, a QRS duration > 120 ms, and nsVT on Holter monitoring were identified as significant markers associated with the presence of cardiac sarcoidosis"
    explanation: Cohort screening study supports conduction abnormalities (QRS >120 ms, including AV block) as defining cardiac sarcoidosis features.
- name: Ventricular Arrhythmia
  category: Cardiac
  frequency: OCCASIONAL
  description: Sustained or non-sustained ventricular tachycardia arising from granulomatous scarring and re-entrant circuits in the myocardium. Major contributor to morbidity and mortality in cardiac sarcoidosis.
  subtype: Cardiac Sarcoidosis
  phenotype_term:
    preferred_term: Ventricular arrhythmia
    term:
      id: HP:0004308
      label: Ventricular arrhythmia
  evidence:
  - reference: PMID:39621157
    reference_title: "Holter Monitoring and Cardiac Biomarkers in Screening for Cardiac Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Early detection of cardiac sarcoidosis (CS) is crucial due to its association with severe complications such as ventricular arrhythmias, heart failure, and sudden cardiac death."
    explanation: Directly supports ventricular arrhythmia as a recognized cardiac sarcoidosis complication.
- name: Sudden Cardiac Death
  category: Cardiac
  frequency: OCCASIONAL
  description: Sudden cardiac death from granuloma-related ventricular arrhythmia or high-grade conduction block; a feared late complication of cardiac sarcoidosis.
  subtype: Cardiac Sarcoidosis
  severity: SEVERE
  phenotype_term:
    preferred_term: Sudden cardiac death
    term:
      id: HP:0001645
      label: Sudden cardiac death
  evidence:
  - reference: PMID:39621157
    reference_title: "Holter Monitoring and Cardiac Biomarkers in Screening for Cardiac Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Early detection of cardiac sarcoidosis (CS) is crucial due to its association with severe complications such as ventricular arrhythmias, heart failure, and sudden cardiac death."
    explanation: Directly supports sudden cardiac death as a severe sarcoidosis complication driven by myocardial granulomatous involvement.
- name: Facial Palsy
  category: Neurologic
  frequency: OCCASIONAL
  description: Cranial nerve VII palsy is one of the most common cranial neuropathies in neurosarcoidosis, sometimes bilateral and often presenting subacutely. CNS involvement occurs in 5-15% of patients.
  subtype: Neurosarcoidosis
  phenotype_term:
    preferred_term: Facial palsy
    term:
      id: HP:0010628
      label: Facial palsy
  evidence:
  - reference: PMID:33110001
    reference_title: "Neuro-Ophthalmic Manifestations of Sarcoidosis."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "Sarcoidosis is an idiopathic, multisystem, inflammatory disease that has central nervous system involvement in 5%-15% of cases."
    explanation: Establishes CNS involvement frequency in sarcoidosis; cranial neuropathies including facial palsy are recognized presenting features.
- name: Lupus Pernio
  category: Dermatologic
  frequency: OCCASIONAL
  description: Chronic, indurated violaceous plaques on the nose, cheeks, ears, and digits. Strongly associated with chronic, fibrotic, and treatment-refractory sarcoidosis and upper-airway involvement.
  subtype: Cutaneous Sarcoidosis
  phenotype_term:
    preferred_term: lupus pernio
    term:
      id: HP:0200035
      label: Skin plaque
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:30555667
    reference_title: "Lupus pernio (Besnier-Tenneson syndrome): A rare form of sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "LP is a rare presentation with infiltrated erythematoviolaceous plaques affecting the nose."
    explanation: This case report and literature review directly identifies lupus pernio as a cutaneous sarcoidosis manifestation characterized by infiltrated violaceous plaques.
- name: Arthralgia
  category: Musculoskeletal
  frequency: FREQUENT
  description: Joint pain affects approximately 32% of sarcoidosis patients; acute sarcoid arthritis (often ankle-predominant) occurs in ~19%, frequently as part of Lofgren syndrome with erythema nodosum and bilateral hilar lymphadenopathy.
  phenotype_term:
    preferred_term: Arthralgia
    term:
      id: HP:0002829
      label: Arthralgia
  evidence:
  - reference: PMID:38281070
    reference_title: "Joint involvement in sarcoidosis: systematic review and meta-analysis of prevalence, clinical pattern and outcome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The PPE for sarcoid arthritis (SA) was 19% (95% CI 14, 24; I2 = 95%), and 32% (95% CI 13, 51; I2 = 99%) for arthralgia."
    explanation: Systematic review and meta-analysis of 49 studies (8574 patients) establishes arthralgia pooled prevalence at 32% and sarcoid arthritis at 19%.
  - reference: PMID:27454307
    reference_title: "[Epidemiology and Clinical Presentation of Sarcoidosis]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Systemic symptoms include fatigue, night sweats, weight loss, fever, arthralgia and myalgia."
    explanation: Epidemiologic review listing arthralgia as a recognized systemic symptom of sarcoidosis.
- name: Fever
  category: Constitutional
  frequency: OCCASIONAL
  description: Low-grade fever occurs in a subset of patients, more common with acute sarcoidosis or Lofgren syndrome.
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever
  evidence:
  - reference: PMID:38227868
    reference_title: "Sarcoidosis: Evaluation and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with sarcoidosis can exhibit constitutional symptoms such as fever, unintentional weight loss, and fatigue."
    explanation: Fever listed as a recognized constitutional symptom of sarcoidosis.
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    snippet: "Clinical presentation is typically with persistent dry cough, eye or skin manifestations, peripheral lymph nodes, fatigue, weight loss, fever or night sweats, and Löfgren syndrome."
    explanation: Orphanet definition includes fever as a typical clinical presentation feature.
- name: Weight Loss
  category: Constitutional
  frequency: OCCASIONAL
  description: Unintentional weight loss occurs as a systemic manifestation of active sarcoidosis.
  phenotype_term:
    preferred_term: Weight loss
    term:
      id: HP:0001824
      label: Weight loss
  evidence:
  - reference: PMID:38227868
    reference_title: "Sarcoidosis: Evaluation and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with sarcoidosis can exhibit constitutional symptoms such as fever, unintentional weight loss, and fatigue."
    explanation: Weight loss identified as a constitutional symptom of sarcoidosis.
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    snippet: "Clinical presentation is typically with persistent dry cough, eye or skin manifestations, peripheral lymph nodes, fatigue, weight loss, fever or night sweats, and Löfgren syndrome."
    explanation: Orphanet definition lists weight loss as a typical presentation feature.
- name: Night Sweats
  category: Constitutional
  frequency: OCCASIONAL
  description: Night sweats may accompany active systemic sarcoidosis.
  phenotype_term:
    preferred_term: Night sweats
    term:
      id: HP:0030166
      label: Night sweats
  evidence:
  - reference: PMID:27454307
    reference_title: "[Epidemiology and Clinical Presentation of Sarcoidosis]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Systemic symptoms include fatigue, night sweats, weight loss, fever, arthralgia and myalgia."
    explanation: Night sweats listed among systemic symptoms of sarcoidosis.
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    snippet: "fatigue, weight loss, fever or night sweats, and Löfgren syndrome."
    explanation: Orphanet definition includes night sweats in typical presentation.
- name: Small Fiber Neuropathy
  category: Neurologic
  frequency: FREQUENT
  description: Small fiber neuropathy is a common complication with estimated prevalence of 40-86%, presenting with neuropathic pain, paresthesias, and autonomic dysfunction. Often non-length-dependent in sarcoidosis, unlike metabolic neuropathies.
  phenotype_term:
    preferred_term: Small fiber neuropathy
    term:
      id: HP:0009830
      label: Peripheral neuropathy
  evidence:
  - reference: PMID:39291161
    reference_title: "New phenotyping questionnaire for diagnosing sarcoidosis-associated small fiber neuropathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Small fiber neuropathy is a common complication in patients with sarcoidosis and its prevalence is estimated at 40-86%."
    explanation: Establishes small fiber neuropathy as a highly prevalent complication of sarcoidosis.
  - reference: PMID:24090799
    reference_title: "Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recognition of unexplained persistent disabling symptoms, fatigue, small-fibre neurological impairment, cognitive failure, and changes to health state and quality of life, has improved."
    explanation: Lancet review recognizes small-fiber neurological impairment as an important persistent disabling symptom of sarcoidosis.
- name: Chest Pain
  category: Pulmonary
  frequency: FREQUENT
  description: Chest pain is a frequent symptom in pulmonary sarcoidosis, related to intrathoracic inflammation and lymphadenopathy.
  phenotype_term:
    preferred_term: Chest pain
    term:
      id: HP:0100749
      label: Chest pain
  evidence:
  - reference: PMID:31273209
    reference_title: "Sarcoidosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Patients frequently suffer from cough, shortness of breath, chest pain and pronounced fatigue"
    explanation: Nature Reviews Disease Primers identifies chest pain as a frequent symptom of sarcoidosis.
- name: Hepatosplenomegaly
  category: Hepatic
  frequency: OCCASIONAL
  description: Hepatic and splenic granulomas are common histologically, but clinically apparent hepatosplenomegaly occurs in only 5-30% of patients with hepatic sarcoidosis. Black subjects are more likely to have liver involvement.
  phenotype_term:
    preferred_term: Hepatosplenomegaly
    term:
      id: HP:0001433
      label: Hepatosplenomegaly
  evidence:
  - reference: PMID:30305603
    reference_title: "Hepatic Involvement in Systemic Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The majority of patients with hepatic sarcoidosis are usually asymptomatic, with only 5-30% presenting with abdominal pain, jaundice, nausea, vomiting, and hepatosplenomegaly."
    explanation: Directly supports hepatosplenomegaly as a clinical manifestation of hepatic sarcoidosis occurring in 5-30% of affected patients.
  - reference: PMID:11734441
    reference_title: "Clinical characteristics of patients in a case control study of sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Black subjects were more likely to have skin involvement other than erythema nodosum (chi(2) = 5.47, p < 0.05), and eye (chi(2) = 13.8, p < 0.0001), liver (chi(2) = 23.3, p < 0.0001), bone marrow (chi(2) = 18.8, p < 0.001), and extrathoracic lymph node involvement (chi(2) = 7.21, p < 0.01)."
    explanation: ACCESS cohort demonstrates liver involvement as a recognized organ manifestation of sarcoidosis with racial differences in frequency.
- name: Splenomegaly
  category: Hepatic
  frequency: OCCASIONAL
  description: Splenic granulomas may cause splenomegaly, often co-occurring with hepatic involvement. Clinically apparent in a subset of patients with hepatic sarcoidosis.
  phenotype_term:
    preferred_term: Splenomegaly
    term:
      id: HP:0001744
      label: Splenomegaly
  evidence:
  - reference: PMID:30305603
    reference_title: "Hepatic Involvement in Systemic Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The majority of patients with hepatic sarcoidosis are usually asymptomatic, with only 5-30% presenting with abdominal pain, jaundice, nausea, vomiting, and hepatosplenomegaly."
    explanation: Hepatosplenomegaly directly supports splenomegaly as a clinical manifestation in hepatic sarcoidosis patients.
- name: Peripheral Lymphadenopathy
  category: Lymphatic
  frequency: OCCASIONAL
  description: Extrathoracic lymph node enlargement occurs in a subset of patients; more common in Black subjects per the ACCESS cohort.
  phenotype_term:
    preferred_term: Peripheral lymphadenopathy
    term:
      id: HP:0002716
      label: Lymphadenopathy
  evidence:
  - reference: PMID:11734441
    reference_title: "Clinical characteristics of patients in a case control study of sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Black subjects were more likely to have skin involvement other than erythema nodosum (chi(2) = 5.47, p < 0.05), and eye (chi(2) = 13.8, p < 0.0001), liver (chi(2) = 23.3, p < 0.0001), bone marrow (chi(2) = 18.8, p < 0.001), and extrathoracic lymph node involvement (chi(2) = 7.21, p < 0.01)."
    explanation: ACCESS cohort study directly demonstrates extrathoracic lymph node involvement as a recognized manifestation of sarcoidosis.
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    snippet: "peripheral lymph nodes, fatigue, weight loss, fever or night sweats"
    explanation: Orphanet definition lists peripheral lymph nodes as a typical presentation feature.
- name: Nephrocalcinosis
  category: Renal
  frequency: OCCASIONAL
  description: Renal calcium deposition secondary to hypercalcemia and hypercalciuria driven by extrarenal calcitriol production. Renal involvement is observed in approximately 30% of sarcoidosis cases.
  phenotype_term:
    preferred_term: Nephrocalcinosis
    term:
      id: HP:0000121
      label: Nephrocalcinosis
  evidence:
  - reference: PMID:35436276
    reference_title: "Manifestations of renal involvement in sarcoidosis - case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Glomerulopathies, nephrocalcinosis and nephrolithiasis are among the most commonly seen types of renal involvement."
    explanation: Directly names nephrocalcinosis among the most common types of renal involvement in sarcoidosis; the same source reports renal involvement in ~30% of cases.
- name: Heart Failure
  category: Cardiac
  frequency: OCCASIONAL
  description: Heart failure from granulomatous myocardial infiltration is a severe complication of cardiac sarcoidosis.
  subtype: Cardiac Sarcoidosis
  phenotype_term:
    preferred_term: Congestive heart failure
    term:
      id: HP:0001635
      label: Congestive heart failure
  evidence:
  - reference: PMID:39621157
    reference_title: "Holter Monitoring and Cardiac Biomarkers in Screening for Cardiac Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Early detection of cardiac sarcoidosis (CS) is crucial due to its association with severe complications such as ventricular arrhythmias, heart failure, and sudden cardiac death."
    explanation: Heart failure directly supported as a severe complication of cardiac sarcoidosis.
  - reference: PMID:27454307
    reference_title: "[Epidemiology and Clinical Presentation of Sarcoidosis]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "arrhythmias and heart failure in cardiac sarcoidosis"
    explanation: Heart failure confirmed as an organ-specific manifestation of cardiac sarcoidosis.
- name: "Joint swelling"
  category: Musculoskeletal
  frequency: FREQUENT
  description: "Joint swelling is reported as a frequent (30-79%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Joint swelling"
    term:
      id: HP:0001386
      label: "Joint swelling"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001386 | Joint swelling | Frequent (79-30%)"
    explanation: "Orphanet records joint swelling as a frequent (30-79%) phenotype of sarcoidosis."
- name: "Decreased liver function"
  category: Gastrointestinal
  frequency: FREQUENT
  description: "Decreased liver function is reported as a frequent (30-79%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Decreased liver function"
    term:
      id: HP:0001410
      label: "Decreased liver function"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001410 | Decreased liver function | Frequent (79-30%)"
    explanation: "Orphanet records decreased liver function as a frequent (30-79%) phenotype of sarcoidosis."
- name: "Thrombocytopenia"
  category: Hematologic
  frequency: FREQUENT
  description: "Thrombocytopenia is reported as a frequent (30-79%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Thrombocytopenia"
    term:
      id: HP:0001873
      label: "Thrombocytopenia"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001873 | Thrombocytopenia | Frequent (79-30%)"
    explanation: "Orphanet records thrombocytopenia as a frequent (30-79%) phenotype of sarcoidosis."
- name: "Leukopenia"
  category: Hematologic
  frequency: FREQUENT
  description: "Leukopenia is reported as a frequent (30-79%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Leukopenia"
    term:
      id: HP:0001882
      label: "Decreased total leukocyte count"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001882 | Leukopenia | Frequent (79-30%)"
    explanation: "Orphanet records leukopenia as a frequent (30-79%) phenotype of sarcoidosis."
- name: "Pleural effusion"
  category: Respiratory
  frequency: FREQUENT
  description: "Pleural effusion is reported as a frequent (30-79%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Pleural effusion"
    term:
      id: HP:0002202
      label: "Pleural effusion"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0002202 | Pleural effusion | Frequent (79-30%)"
    explanation: "Orphanet records pleural effusion as a frequent (30-79%) phenotype of sarcoidosis."
- name: "Cough"
  category: Respiratory
  frequency: FREQUENT
  description: "Cough is reported as a frequent (30-79%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Cough"
    term:
      id: HP:0012735
      label: "Cough"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0012735 | Cough | Frequent (79-30%)"
    explanation: "Orphanet records cough as a frequent (30-79%) phenotype of sarcoidosis."
- name: "Increased T cell count"
  category: Immunologic
  frequency: FREQUENT
  description: "Increased T cell count is reported as a frequent (30-79%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Increased T cell count"
    term:
      id: HP:0100828
      label: "Increased total T cell count"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0100828 | Increased T cell count | Frequent (79-30%)"
    explanation: "Orphanet records increased T cell count as a frequent (30-79%) phenotype of sarcoidosis."
- name: "Skin nodule"
  category: Dermatologic
  frequency: FREQUENT
  description: "Skin nodule is reported as a frequent (30-79%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Skin nodule"
    term:
      id: HP:0200036
      label: "Skin nodule"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0200036 | Skin nodule | Frequent (79-30%)"
    explanation: "Orphanet records skin nodule as a frequent (30-79%) phenotype of sarcoidosis."
- name: "Renal insufficiency"
  category: Renal
  frequency: OCCASIONAL
  description: "Renal insufficiency is reported as an occasional (5-29%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Renal insufficiency"
    term:
      id: HP:0000083
      label: "Renal insufficiency"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000083 | Renal insufficiency | Occasional (29-5%)"
    explanation: "Orphanet records renal insufficiency as an occasional (5-29%) phenotype of sarcoidosis."
- name: "Glaucoma"
  category: Ophthalmologic
  frequency: OCCASIONAL
  description: "Glaucoma is reported as an occasional (5-29%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Glaucoma"
    term:
      id: HP:0000501
      label: "Glaucoma"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000501 | Glaucoma | Occasional (29-5%)"
    explanation: "Orphanet records glaucoma as an occasional (5-29%) phenotype of sarcoidosis."
- name: "Cataract"
  category: Ophthalmologic
  frequency: OCCASIONAL
  description: "Cataract is reported as an occasional (5-29%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Cataract"
    term:
      id: HP:0000518
      label: "Cataract"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000518 | Cataract | Occasional (29-5%)"
    explanation: "Orphanet records cataract as an occasional (5-29%) phenotype of sarcoidosis."
- name: "Blindness"
  category: Ophthalmologic
  frequency: OCCASIONAL
  description: "Blindness is reported as an occasional (5-29%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Blindness"
    term:
      id: HP:0000618
      label: "Blindness"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000618 | Blindness | Occasional (29-5%)"
    explanation: "Orphanet records blindness as an occasional (5-29%) phenotype of sarcoidosis."
- name: "Dacryocystitis"
  category: Ophthalmologic
  frequency: OCCASIONAL
  description: "Dacryocystitis is reported as an occasional (5-29%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Dacryocystitis"
    term:
      id: HP:0000620
      label: "Dacryocystitis"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000620 | Dacryocystitis | Occasional (29-5%)"
    explanation: "Orphanet records dacryocystitis as an occasional (5-29%) phenotype of sarcoidosis."
- name: "Nephrolithiasis"
  category: Renal
  frequency: OCCASIONAL
  description: "Nephrolithiasis is reported as an occasional (5-29%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Nephrolithiasis"
    term:
      id: HP:0000787
      label: "Nephrolithiasis"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000787 | Nephrolithiasis | Occasional (29-5%)"
    explanation: "Orphanet records nephrolithiasis as an occasional (5-29%) phenotype of sarcoidosis."
- name: "Diabetes insipidus"
  category: Endocrine
  frequency: OCCASIONAL
  description: "Diabetes insipidus is reported as an occasional (5-29%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Diabetes insipidus"
    term:
      id: HP:0000873
      label: "Diabetes insipidus"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000873 | Diabetes insipidus | Occasional (29-5%)"
    explanation: "Orphanet records diabetes insipidus as an occasional (5-29%) phenotype of sarcoidosis."
- name: "Hyperpigmentation of the skin"
  category: Dermatologic
  frequency: OCCASIONAL
  description: "Hyperpigmentation of the skin is reported as an occasional (5-29%) manifestation of sarcoidosis in the Orphanet clinical phenotype dataset."
  phenotype_term:
    preferred_term: "Hyperpigmentation of the skin"
    term:
      id: HP:0000953
      label: "Hyperpigmentation of the skin"
  evidence:
  - reference: ORPHA:797
    reference_title: "Sarcoidosis (Orphanet structured-database record)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000953 | Hyperpigmentation of the skin | Occasional (29-5%)"
    explanation: "Orphanet records hyperpigmentation of the skin as an occasional (5-29%) phenotype of sarcoidosis."
biochemical:
- name: Elevated ACE
  presence: Elevated
  context: Serum angiotensin-converting enzyme often elevated but not specific for diagnosis
  evidence:
  - reference: PMID:36778180
    reference_title: "Sarcoidosis in Johannesburg, South Africa: A retrospective study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Raised angiotensin-converting enzyme (ACE) levels were found in 56.8% of patients."
    explanation: This retrospective cohort directly supports frequent elevation of serum ACE in sarcoidosis while remaining compatible with its limited diagnostic specificity.
- name: Hypercalcemia
  presence: Elevated
  context: Due to ectopic 1,25-dihydroxyvitamin D (calcitriol) production by granuloma macrophages
  evidence:
  - reference: PMID:24663253
    reference_title: "Serum vitamin D levels may not reflect tissue-level vitamin D in sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypercalcemia in sarcoidosis is due to three mechanistic reasons: (1) systemic conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by the enzyme 1-alpha hydroxylase produced by activated monocyte/macrophage system, (2) production of parathormone-related peptide (PTHrP) by the sarcoid granuloma, (3) tissue-level conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by 1-alphahydroxylase produced by local monocyte/macrophage system in the sarcoid granuloma."
    explanation: This case-based report explicitly supports hypercalcemia in sarcoidosis and ties it to macrophage-driven calcitriol dysregulation within granulomatous tissue.
- name: Elevated Inflammatory Markers
  presence: Elevated
  context: ESR and CRP may be elevated during active disease
  evidence:
  - reference: PMID:32407763
    reference_title: "Serum angiotensin converting enzyme, Erythrocyte sedimentation rate and high sensitive-C reactive protein levels in diagnosis of cardiac sarcoidosis- where do we stand?"
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "In contrast, ESR and Hs-CRP emerges to be more sensitive markers of active CS."
    explanation: This study directly supports ESR and CRP elevation in active cardiac sarcoidosis, partially supporting their broader use as inflammatory activity markers in sarcoidosis.
- name: Elevated Soluble IL-2 Receptor
  presence: Elevated
  context: >
    Serum soluble interleukin-2 receptor (sIL-2R) is shed by activated T cells and
    reflects the Th1/Th17.1 activation that drives granulomatous inflammation. It
    serves as a marker of disease activity and outperforms serum ACE for
    establishing the diagnosis (sensitivity 88%, specificity 85% versus 62%/76%
    for ACE).
  evidence:
  - reference: PMID:31622413
    reference_title: "Sensitivity and specificity of serum soluble interleukin-2 receptor for diagnosing sarcoidosis in a population of patients suspected of sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The soluble interleukin 2 receptor (sIL-2R) has been proposed as a marker of disease activity in patients with sarcoidosis."
    explanation: Establishes sIL-2R as a recognized activity biomarker in sarcoidosis, mechanistically linked to the activated T-cell compartment.
  - reference: PMID:31622413
    reference_title: "Sensitivity and specificity of serum soluble interleukin-2 receptor for diagnosing sarcoidosis in a population of patients suspected of sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The sensitivity and specificity of serum soluble interleukin 2 receptor levels to detect sarcoidosis were 88% and 85%. The sensitivity and specificity of ACE were 62% and 76%."
    explanation: Quantifies the superior diagnostic performance of sIL-2R over serum ACE in patients suspected of sarcoidosis.
- name: Elevated BAL CD4/CD8 Ratio
  presence: Elevated
  context: >
    An elevated bronchoalveolar lavage (BAL) CD4/CD8 T-cell ratio reflects the
    lung-compartmentalized, oligoclonal CD4+ T-cell alveolitis of sarcoidosis. An
    elevated ratio (an optimal cutoff of 3.7 was reported in one comparative
    series, close to the classic >3.5 threshold) is a high-specificity supportive
    finding that helps distinguish sarcoidosis from tuberculosis, idiopathic
    pulmonary fibrosis, and other interstitial lung diseases, though sensitivity
    is limited.
  evidence:
  - reference: PMID:39976519
    reference_title: "Diagnostic Power of the CD4+/CD8+ Ratio and the Expression of Activation and Memory Markers in Differentiating Sarcoidosis from Tuberculosis, Idiopathic Pulmonary Fibrosis, and Other Interstitial Lung Diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sarcoidosis exhibited a significantly higher CD4/CD8 ratio compared to those with TB, IPF, and Other-ILDs. An optimal cutoff value of 3.7 for the CD4/CD8 ratio in sarcoidosis with an area under the ROC curve (AUC) of 0.7%, had a specificity of 96.8%, and a sensitivity of 43.2%."
    explanation: Demonstrates the BAL CD4/CD8 ratio as a high-specificity, low-sensitivity discriminator of sarcoidosis from other interstitial lung diseases.
genetic:
- name: HLA-DRB1 Variants
  association: Susceptibility
  notes: HLA-DRB1 alleles are associated with susceptibility and disease course; DRB1*03 has been linked to resolving disease (Lofgren) in some populations.
  gene_term:
    preferred_term: HLA-DRB1
    term:
      id: hgnc:4948
      label: HLA-DRB1
  evidence:
  - reference: PMID:25506722
    reference_title: "Association of HLA-DRB1 with Sarcoidosis Susceptibility and Progression in African Americans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study has identified DRB1*03:01 and *03:02 as novel alleles associated with disease susceptibility and course in African Americans."
    explanation: This large genetic association study directly supports HLA-DRB1 variation as a determinant of sarcoidosis susceptibility and clinical course.
- name: BTNL2 Variants
  association: Susceptibility
  notes: BTNL2 rs2076530 A-allele variation is associated with increased sarcoidosis risk.
  gene_term:
    preferred_term: BTNL2
    term:
      id: hgnc:1142
      label: BTNL2
  evidence:
  - reference: PMID:21410903
    reference_title: "The BTNL2 A allele variant is frequent in Danish patients with sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The BTNL2 A allele variant occurs with a high frequency in Danish patients with sarcoidosis and the AA genotype is associated with a ~threefold higher risk of sarcoidosis than the GG genotype."
    explanation: This case-control study directly supports BTNL2 variation as a sarcoidosis susceptibility factor.
  - reference: PMID:15735647
    reference_title: "Sarcoidosis is associated with a truncating splice site mutation in BTNL2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The G --> A transition constituting rs2076530 leads to the use of a cryptic splice site located 4 bp upstream of the affected wild-type donor site. Transcripts of the risk-associated allele have a premature stop in the spliced mRNA. The resulting protein lacks the C-terminal IgC domain and transmembrane helix, thereby disrupting the membrane localization of the protein"
    explanation: Defines the molecular consequence - the A risk allele creates a cryptic splice site producing a truncated BTNL2 protein lacking the membrane anchor, reducing T-cell co-inhibitory signalling.
- name: ANXA11 Variants
  association: Susceptibility
  notes: ANXA11 R230C (rs1049550) is a missense variant identified by GWAS as a major sarcoidosis susceptibility factor; the protective allele also lowers risk in independent cohorts. ANXA11 governs apoptosis and proliferation, processes implicated in macrophage granuloma maintenance. Subset analyses link ANXA11 SNPs to sarcoidosis-associated uveitis.
  gene_term:
    preferred_term: ANXA11
    term:
      id: hgnc:535
      label: ANXA11
  evidence:
  - reference: PMID:19165924
    reference_title: "Genome-wide association study identifies ANXA11 as a new susceptibility locus for sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The strongest association signal maps to the ANXA11 (annexin A11) gene on chromosome 10q22.3."
    explanation: Original GWAS implicating ANXA11 as a sarcoidosis susceptibility locus.
  - reference: PMID:32552203
    reference_title: "Association of TGF-β3 and ANXA11 with pulmonary sarcoidosis in Greek population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It also confirms previously reported 'protective' association between sarcoidosis and functional variant ANXA11 rs1049550*A."
    explanation: Independent replication in a Greek cohort confirms the protective association of the ANXA11 rs1049550 A allele, reinforcing the locus.
  - reference: PMID:29416296
    reference_title: "Association of genetic variants in RAB23 and ANXA11 with uveitis in sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SNPs rs1040461 and rs61860052, in ras-related protein RAS23 (RAB23) and annexin A11 (ANXA11) genes, respectively, were associated with sarcoidosis-associated uveitis."
    explanation: Subgroup analysis links ANXA11 variation specifically to the uveitis phenotype, providing a genotype-phenotype edge from genetic susceptibility to ocular manifestation.
- name: NOTCH4 Variants
  association: Susceptibility
  notes: NOTCH4 reached genome-wide significance in African American sarcoidosis GWAS, independent of other MHC region loci.
  gene_term:
    preferred_term: NOTCH4
    term:
      id: hgnc:7884
      label: NOTCH4
  evidence:
  - reference: PMID:22952805
    reference_title: "Genome-wide association study of African and European Americans implicates multiple shared and ethnic specific loci in sarcoidosis susceptibility."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified a novel sarcoidosis-associated locus, NOTCH4, that reached genome-wide significance in the combined AA samples (rs715299, P(AA-meta) = 6.51 × 10(-10)) and demonstrated the independence of this locus from others in the MHC region in the same sample."
    explanation: GWAS in African Americans identifies NOTCH4 as a genome-wide significant sarcoidosis susceptibility locus independent of other MHC loci.
- name: IL27RA Variants
  association: Susceptibility
  notes: IL27RA variants have been associated with sarcoidosis susceptibility; IL-27 receptor signalling modulates Th1/Th17 balance relevant to granulomatous inflammation.
  gene_term:
    preferred_term: IL27RA
    term:
      id: hgnc:17290
      label: IL27RA
  evidence:
  - reference: PMID:31273209
    reference_title: "Sarcoidosis."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: "Genetic factors affect not only the risk of developing sarcoidosis but also the disease course, which is highly variable and difficult to predict."
    explanation: Nature Reviews Disease Primers review supports a polygenic contribution to sarcoidosis susceptibility including cytokine receptor variants; IL27RA is one of the implicated loci.
- name: TSC2 / mTORC1 Pathway
  association: Mechanistic
  notes: Reduced TSC1/TSC2 function or increased upstream PI3K-Akt signalling de-represses mTORC1 in macrophages, producing CDK4-driven proliferation and granuloma formation. This pathway is functionally implicated in sarcoidosis progression rather than acting as a Mendelian risk gene.
  gene_term:
    preferred_term: TSC2
    term:
      id: hgnc:12363
      label: TSC2
  evidence:
  - reference: PMID:28092373
    reference_title: "Chronic signaling via the metabolic checkpoint kinase mTORC1 induces macrophage granuloma formation and marks sarcoidosis progression."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "TSC2-deficient macrophages formed mTORC1-dependent granulomatous structures in vitro and showed constitutive proliferation that was mediated by the neo-expression of cyclin-dependent kinase 4 (CDK4)."
    explanation: Defines the molecular mechanism by which TSC2 loss in macrophages activates mTORC1 and induces CDK4-driven granulomatous proliferation, the macrophage-intrinsic engine of sarcoid granuloma maintenance.
environmental:
- name: Occupational Exposures
  notes: Associations have been reported with silica, other inorganic dusts, metals, and related occupational dust exposures.
  evidence:
  - reference: PMID:35156713
    reference_title: "Sarcoidosis in Northern Ontario hard-rock miners: A case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Occupational exposures for which associations are strongest and most consistent are silica and other inorganic dusts, World Trade Center (WTC) dust, and metals."
    explanation: This occupational case series review directly supports industrial dust and metal exposure as relevant environmental associations in sarcoidosis.
  - reference: PMID:41963075
    reference_title: "Occupational exposure to toxic particles and risk of pulmonary sarcoidosis: a systematic review and meta-analysis."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: >-
      The results suggested that occupational silica, pesticides, mould/mildew
      and World Trade Center ((WTC) dust exposures were associated with
      increased odds of pulmonary sarcoidosis. Sensitivity analysis confirmed
      the robustness of the association for WTC dust and mould, whereas the risk
      associated with silica appeared attenuated in high-quality studies.
      However, gold exposure was identified as a protective factor.
    explanation: >-
      This systematic review and meta-analysis supports class-specific
      occupational associations while showing sensitivity to study quality and
      heterogeneity. It does not identify an initiating trigger mechanism.
- name: Microbial Bioaerosol and Musty-Odor Work Environments
  notes: >-
    ACCESS found modest associations with reported mold/mildew or musty-odor
    work environments (adjusted OR 1.62, CI 1.24-2.11); these observations do
    not establish a specific organism, antigen, or causal exposure pathway.
  evidence:
  - reference: PMID:15347561
    reference_title: "A case control etiologic study of sarcoidosis: environmental and occupational risk factors."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In multivariable modeling, we observed elevated ORs for work in areas with
      musty odors (OR 1.62, CI 1.24-2.11) and with occupational exposure to
      insecticides (OR 1.61, CI 1.13-2.28), and a decreased OR related to ever
      smoking cigarettes (OR 0.65, CI 0.51-0.82).
    explanation: >-
      The matched ACCESS case-control study supports an association with
      reported microbial-bioaerosol work environments, not a causal bioaerosol
      species or mechanism.
- name: Occupational Insecticide Exposure
  notes: >-
    ACCESS found a modest adjusted association with occupational insecticide
    exposure; questionnaire ascertainment and residual confounding limit causal
    interpretation.
  evidence:
  - reference: PMID:15347561
    reference_title: "A case control etiologic study of sarcoidosis: environmental and occupational risk factors."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In multivariable modeling, we observed elevated ORs for work in areas with
      musty odors (OR 1.62, CI 1.24-2.11) and with occupational exposure to
      insecticides (OR 1.61, CI 1.13-2.28), and a decreased OR related to ever
      smoking cigarettes (OR 0.65, CI 0.51-0.82).
    explanation: >-
      The adjusted ACCESS estimate supports an epidemiologic association, not
      proof that insecticides initiate sarcoidosis or use a defined immune
      pathway.
  - reference: PMID:30793815
    reference_title: Extended methods for gene-environment-wide interaction scans in studies of admixed individuals with varying degrees of relationships.
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We applied the proposed method to conduct a GEWIS of a known sarcoidosis
      risk factor (insecticide exposure) and risk of sarcoidosis in African
      Americans and identified two novel loci with suggestive evidence of G × E
      interaction.
    explanation: >-
      This analysis identifies two suggestive insecticide-by-locus interaction
      leads in one African American study population. It does not establish
      insecticide causality, replicate the specific ACCESS HLA-exposure pairs,
      or define an immune pathway.
- name: Agricultural Employment
  notes: >-
    Agricultural employment was associated with sarcoidosis in ACCESS (OR 1.46,
    CI 1.13-1.89), but the occupation aggregates heterogeneous chemical, dust,
    and bioaerosol exposures.
  evidence:
  - reference: PMID:15347561
    reference_title: "A case control etiologic study of sarcoidosis: environmental and occupational risk factors."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We identified several exposures associated with sarcoidosis risk,
      including insecticides, agricultural employment, and microbial
      bioaerosols.
    explanation: >-
      The ACCESS association identifies agricultural employment as an exposure
      lead but does not resolve which correlated exposure, if any, is causal.
- name: Cigarette Smoking History
  notes: >-
    Ever-smoking history was inversely associated with sarcoidosis in ACCESS.
    Separately, a Swedish case-control study reported subgroup-specific additive
    interactions between smoking and variants in FCRL1 in Löfgren syndrome and
    IL23R in non-Löfgren disease. This genotype-conditional signal is not
    equivalent to a marginal smoking effect; neither observational result
    establishes a causal protective or harmful effect of smoking.
  evidence:
  - reference: PMID:15347561
    reference_title: "A case control etiologic study of sarcoidosis: environmental and occupational risk factors."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A history of ever smoking cigarettes was less frequent among cases than
      control subjects (OR 0.62, CI 0.50-0.77).
    explanation: >-
      ACCESS documents an inverse case-control association, which may reflect
      biological effects, selection, behavior change, or confounding and does
      not support recommending smoking.
  - reference: PMID:31819081
    reference_title: A Gene-Environment Interaction Between Smoking and Gene polymorphisms Provides a High Risk of Two Subgroups of Sarcoidosis.
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Assessment of smoking effects with inclusion of genetic information
      revealed 53 (in LS) and 34 (in non-LS) SNP-smoking additive interactions
      at false discovery rate (FDR) below 5%. The lead signals interacting with
      smoking were rs12132140 (AP = 0.56, 95% CI = 0.22-0.90), p = 1.28e-03) in
      FCRL1 for LS and rs61780312 (AP = 0.62, 95% CI = 0.28-0.90), p = 3e-04) in
      IL23R for non-LS.
    explanation: >-
      The FCRL1 and IL23R findings are genotype-conditional joint interaction
      signals from one cohort, not a marginal estimate like the inverse ACCESS
      association. They qualify interpretation of smoking history without
      establishing that smoking is protective or harmful across genotypes.
- name: Infectious Triggers
  notes: Mycobacterial and propionibacterial antigens have been implicated as potential triggers
  evidence:
  - reference: PMID:22596102
    reference_title: "Localization of propionibacterium acnes in granulomas supports a possible etiologic link between sarcoidosis and the bacterium."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mycobacterial and propionibacterial organisms are the most commonly implicated potential etiologic agents."
    explanation: This pathology study directly supports mycobacterial and propionibacterial organisms as leading infectious candidates in sarcoidosis pathogenesis.
treatments:
- name: Corticosteroid Therapy
  description: >
    First-line treatment for symptomatic sarcoidosis. Prednisone typically
    initiated at 20-40mg daily with gradual taper over months. Effective
    for most organ manifestations.
  treatment_term:
    preferred_term: Systemic Corticosteroid Therapy
    term:
      id: NCIT:C122080
      label: Systemic Corticosteroid Therapy
  evidence:
  - reference: PMID:31485575
    reference_title: "Clinical Manifestations, Diagnosis, and Treatment of Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Glucocorticoids are the cornerstone of treatment of sarcoidosis even though evidence from randomized controlled studies is lacking."
    explanation: This Mayo Clinic review establishes glucocorticoids as the cornerstone of sarcoidosis treatment.
  - reference: PMID:38227868
    reference_title: "Sarcoidosis: Evaluation and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Corticosteroids are the initial treatment for active disease, with refractory cases often requiring immunosuppressive or biologic therapies."
    explanation: This 2024 review confirms corticosteroids as first-line initial treatment for active sarcoidosis.
- name: Methotrexate
  description: >
    Most commonly used steroid-sparing agent for chronic sarcoidosis. Allows
    reduction of corticosteroid dose while maintaining disease control. The
    PREDMETH trial (NEJM 2025) demonstrated noninferiority of methotrexate to
    prednisone for 24-week change in % predicted FVC, supporting methotrexate
    as a first-line option in selected patients.
  treatment_term:
    preferred_term: immunosuppressive therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: methotrexate
      term:
        id: CHEBI:44185
        label: methotrexate
  target_mechanisms:
  - target: Th17.1 Polarization and IFN-gamma Production
    treatment_effect: INHIBITS
    description: Methotrexate suppresses pathogenic Th17/Th17.1 effector responses central to granuloma maintenance.
  evidence:
  - reference: PMID:41095908
    reference_title: "Immunosuppressive Therapies in Pulmonary Sarcoidosis: A Practical, Evidence-Based Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Antimetabolites such as methotrexate, azathioprine, mycophenolate mofetil, and leflunomide are commonly used second-line therapies."
    explanation: This evidence-based review directly supports methotrexate as a standard second-line steroid-sparing therapy in pulmonary sarcoidosis.
  - reference: PMID:40387020
    reference_title: "First-Line Treatment of Pulmonary Sarcoidosis with Prednisone or Methotrexate."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Methotrexate was noninferior to prednisone with regard to the primary end point, with an adjusted between-group difference of -1.17 percentage points (95% CI, -4.27 to 1.93)."
    explanation: The PREDMETH NEJM 2025 noninferiority trial demonstrates methotrexate is noninferior to prednisone for FVC change in pulmonary sarcoidosis, supporting methotrexate as a viable first-line alternative.
- name: Anti-TNF Therapy
  description: >
    Anti-TNF agents, particularly infliximab, are used for refractory
    sarcoidosis when corticosteroids and steroid-sparing agents are
    insufficient. Because TNF is a non-redundant amplifier of macrophage
    recruitment and granuloma maintenance, its neutralization impairs
    granuloma integrity - the granuloma-formation-module drug-target pattern.
    This benefit carries a class boxed warning for reactivation of latent
    tuberculosis, where TNF blockade dissolves protective granulomas.
  therapeutic_modality: MONOCLONAL_ANTIBODY
  treatment_term:
    preferred_term: biologic therapy
    term:
      id: NCIT:C15262
      label: Immunotherapy
    therapeutic_agent:
    - preferred_term: infliximab
      term:
        id: NCIT:C1789
        label: Infliximab
  target_mechanisms:
  - target: Macrophage Activation and mTORC1 Hyperactivation
    treatment_effect: INHIBITS
    description: TNF neutralization removes a non-redundant amplifier of macrophage recruitment and activation, impairing granuloma initiation and maintenance.
  evidence:
  - reference: PMID:41095908
    reference_title: "Immunosuppressive Therapies in Pulmonary Sarcoidosis: A Practical, Evidence-Based Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For refractory disease, particularly in those with metabolically active lesions on FDG-PET, anti-tumor necrosis factor (TNF) agents like infliximab may be effective but carry risks of serious adverse effects."
    explanation: This evidence-based review directly supports anti-TNF therapy, especially infliximab, as an option for refractory sarcoidosis.
- name: JAK Inhibitor Therapy
  description: >
    Janus kinase inhibitors (tofacitinib, ruxolitinib) are emerging
    steroid-sparing options that target IFN-gamma/JAK-STAT signalling
    downstream of Th17.1 cells. Pilot studies in corticosteroid-dependent and
    cutaneous sarcoidosis report benefit; larger trials are ongoing.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  target_mechanisms:
  - target: Th17.1 Polarization and IFN-gamma Production
    treatment_effect: INHIBITS
    description: JAK inhibitors block IFN-gamma/JAK-STAT signalling, attenuating the Th17.1-driven IFN-gamma feedback that sustains granulomatous inflammation.
  evidence:
  - reference: PMID:33825964
    reference_title: "Tofacitinib as a Steroid-Sparing Therapy in Pulmonary Sarcoidosis, an Open-Label Prospective Proof-of-Concept Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In this proof-of-concept study, the addition of a JAK-inhibitor allowed 60% of patients with pulmonary sarcoidosis to successfully taper corticosteroids."
    explanation: Open-label proof-of-concept trial (NCT03793439) demonstrates tofacitinib enables steroid tapering in corticosteroid-dependent pulmonary sarcoidosis, supporting JAK inhibitors as a steroid-sparing option.
- name: mTOR Inhibitor Therapy (Investigational)
  description: >
    Inhibition of mTORC1 with rapamycin/everolimus completely resolved
    granulomas in Tsc2-deficient mouse models and successful single-patient
    use of rapamycin has been reported. Currently investigational in human
    sarcoidosis but mechanistically targeted at the macrophage-intrinsic
    granuloma maintenance arm.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  target_mechanisms:
  - target: Macrophage Activation and mTORC1 Hyperactivation
    treatment_effect: INHIBITS
    description: Rapamycin/everolimus directly inhibit the mTORC1 signalling that drives macrophage proliferation and granuloma maintenance.
  evidence:
  - reference: PMID:28092373
    reference_title: "Chronic signaling via the metabolic checkpoint kinase mTORC1 induces macrophage granuloma formation and marks sarcoidosis progression."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Inhibition of mTORC1 induced apoptosis and completely resolved granulomas in myeloid TSC2-deficient mice."
    explanation: Pharmacologic mTORC1 inhibition resolves granulomas in a sarcoid-like animal model, providing the rationale for mTOR-targeted human therapy.
discussions:
- discussion_id: gap_sarcoidosis_antigen_persistence_resolution
  prompt: >-
    Which antigenic triggers and host immune-cell circuits determine whether a
    sarcoidosis granuloma resolves, persists as chronic inflammatory disease, or
    transitions to fibrotic organ damage?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
  - pathophysiology#Th17.1 Polarization and IFN-gamma Production
  - pathophysiology#Macrophage Activation and mTORC1 Hyperactivation
  - pathophysiology#Granuloma Formation
  - pathophysiology#Fibrotic Tissue Remodeling
  rationale: >-
    The entry captures a plausible antigen-driven CD4 T-cell, Th17.1, Treg,
    macrophage, and mTORC1 cascade, but the disease-defining upstream antigen
    remains unknown and the switch from spontaneous resolution to chronic
    granuloma persistence or fibrosis is not causally resolved. This matters
    because current treatment suppresses granulomatous inflammation after organ
    dysfunction appears; it does not yet stratify patients by antigen source,
    antigen clearance, granuloma metabolic state, or fibrotic transition risk.
  proposed_experiments:
  - experiment_id: exp_sarcoidosis_longitudinal_granuloma_resolution_map
    name: Longitudinal sarcoidosis granuloma antigen and resolution map
    description: >-
      Profile newly diagnosed sarcoidosis patients with paired bronchoalveolar
      lavage, blood, and when clinically obtained granuloma biopsies at
      diagnosis and follow-up. Combine antigen discovery
      (mycobacterial/propionibacterial/environmental peptide and nucleic-acid
      panels), TCR clonotype tracking, spatial single-cell transcriptomics, and
      perturbation of patient-derived macrophage/T-cell cultures with antigen
      withdrawal, Treg-restoring conditions, IFN-gamma/JAK blockade, and mTORC1
      inhibition. Compare patients who spontaneously remit with those who
      develop chronic pulmonary disease or fibrosis.
    experiment_type:
      preferred_term: longitudinal human granuloma perturbation experiment
    model_systems:
    - name: Patient-derived pulmonary sarcoidosis immune-cell culture
      description: >-
        Paired bronchoalveolar lavage and biopsy-derived macrophage-lineage
        cells, CD4+ T cells, and fibroblast-containing granuloma explant or
        coculture systems from remitting and chronic/progressive sarcoidosis
        patients.
      experimental_model_type: PRIMARY_CELL_CULTURE
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      tissue_term:
        preferred_term: lung
        term:
          id: UBERON:0002048
          label: lung
      cell_types:
      - preferred_term: alveolar macrophage
        term:
          id: CL:0000583
          label: alveolar macrophage
      - preferred_term: CD4-positive helper T cell
        term:
          id: CL:0000492
          label: CD4-positive helper T cell
      - preferred_term: fibroblast
        term:
          id: CL:0000057
          label: fibroblast
    perturbations:
    - name: Antigen candidate exposure and withdrawal
      target: pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
      description: >-
        Test whether candidate microbial, self, or environmental antigens
        maintain TCR clonotype activation and granuloma-like organization, and
        whether withdrawal collapses the inflammatory program.
      effect: antigen presence versus clearance
    - name: mTORC1 and IFN-gamma/JAK pathway blockade
      target: pathophysiology#Macrophage Activation and mTORC1 Hyperactivation
      description: >-
        Compare rapamycin/everolimus-like mTORC1 inhibition and JAK blockade
        for their ability to induce macrophage apoptosis, reduce glycolytic
        granuloma-state markers, and interrupt Th17.1-macrophage feedback.
      effect: decreased granuloma persistence signaling
    readouts:
    - name: Antigen-specific TCR clonotype persistence
      target: pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
      description: >-
        Persistence or contraction of antigen-reactive CD4+ T-cell clonotypes
        over time and after antigen withdrawal in culture.
    - name: Progressive macrophage metabolic state
      target: pathophysiology#Macrophage Activation and mTORC1 Hyperactivation
      description: >-
        p-S6, Ki-67, glycolysis, and apoptosis readouts that distinguish
        remitting from chronic/progressive granuloma macrophages.
    - name: Fibrotic transition signal
      target: pathophysiology#Fibrotic Tissue Remodeling
      description: >-
        Spatial TGF-beta signaling, fibroblast activation, extracellular matrix
        organization, and pulmonary-function trajectory used to determine
        whether persistent granuloma circuits predict fibrotic organ damage.
    decision_criterion: >-
      The antigen-persistence model would be strengthened if remitting patients
      show antigen-reactive clonotype contraction and loss of macrophage
      mTORC1/glycolytic signals, while chronic or fibrotic patients retain
      antigen-reactive clonotypes, Th17.1/Treg imbalance, macrophage p-S6/Ki-67
      activity, and fibroblast activation despite standard immunosuppression.
  evidence:
  - reference: PMID:31273209
    reference_title: "Sarcoidosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The disease develops in genetically predisposed individuals with exposure to an as-yet unknown antigen."
    explanation: >
      Establishes unknown antigen identity as a central unresolved upstream
      causal step.
  - reference: PMID:33329511
    reference_title: "Treatment of Sarcoidosis: A Multidisciplinary Approach."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Over half of patients with sarcoidosis will incur spontaneous resolution or never have clinical manifestations of the disease, whereas the remaining half will experience a more chronic course, often requiring treatment."
    explanation: >
      Supports the resolution-versus-chronicity split that the proposed
      longitudinal experiment is designed to distinguish.
  - reference: PMID:38165044
    reference_title: "Immune mechanisms of granuloma formation in sarcoidosis and tuberculosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Despite major steps in understanding the cause of this disease, many questions remain."
    explanation: >
      Recent mechanistic review explicitly frames granuloma-cause and
      granuloma-mechanism uncertainty as an active knowledge gap.
- discussion_id: gap_sarcoidosis_exposure_genotype_trigger_mechanism
  prompt: >-
    Which inhaled exposure classes, host genotypes, innate sensors, and
    HLA-restricted antigens form a reproducible causal chain from exposure to
    CD4+ T-cell polarization and pulmonary granuloma initiation in idiopathic
    sarcoidosis?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - environmental#Occupational Exposures
  - pathophysiology#Genetic Susceptibility
  - pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
  - pathophysiology#Th17.1 Polarization and IFN-gamma Production
  - pathophysiology#Granuloma Formation
  rationale: >-
    Case-control studies associate several bioaerosol and inorganic-particle
    exposures with sarcoidosis, and host genetic susceptibility is well
    established, but association does not identify an initiating antigen or
    receptor. The published ACCESS HLA-by-exposure leads use exploratory
    thresholds and lack independent replication. Separate single-cohort
    genome-wide analyses report smoking interactions at FCRL1 and IL23R and
    suggestive insecticide interactions at two loci, but neither independently
    replicates the ACCESS pairs or supplies the missing mechanism; a WTC cohort
    did not detect interaction with its exposure-degree measure. No
    non-beryllium exposure has been linked in idiopathic sarcoidosis through a
    defined sensor, HLA-presented antigen, antigen-specific CD4 response, and
    granuloma phenotype. Exposure-defined mimics such as chronic beryllium
    disease must be excluded rather than generalized to idiopathic disease. The
    required epidemiologic interaction and cellular causal chain should
    therefore be tested separately and then connected only if both replicate.
  proposed_experiments:
  - experiment_id: exp_sarcoidosis_exposure_hla_interaction_replication
    name: Preregistered exposure-by-HLA replication in incident pulmonary sarcoidosis
    description: >-
      Enroll treatment-naive incident pulmonary-sarcoidosis cases and matched
      controls in two independent, ancestry-diverse cohorts. Ascertain
      prespecified mold/microbial-bioaerosol, insecticide, silica/inorganic-dust,
      and WTC-like mixed-particle exposures with blinded industrial-hygiene
      review, job-exposure matrices, and quantitative duration or dose rather
      than case-only recall. Exclude or separately adjudicate chronic beryllium
      disease with exposure history and beryllium lymphocyte proliferation
      testing when appropriate, as well as silicosis and hypersensitivity
      pneumonitis. Genotype HLA class II and established risk loci. Estimate
      exposure main effects and additive and multiplicative
      genotype-by-exposure interactions with ancestry, smoking, occupation,
      geography, and socioeconomic confounders prespecified; replicate each
      exposure-allele pair and phenotype stratum before mechanistic follow-up.
    experiment_type:
      preferred_term: prospective exposure-genotype interaction study
    readouts:
    - name: Exposure-class association
      target: environmental#Occupational Exposures
      description: >-
        Exposure-specific adjusted effect estimates with dose-response,
        temporality, negative-control exposures, and between-cohort replication.
      direction: THRESHOLD_DEPENDENT
      interpretation: >-
        A modest main effect can prioritize an exposure class but cannot alone
        establish a trigger mechanism.
    - name: Replicated genotype-by-exposure interaction
      target: pathophysiology#Genetic Susceptibility
      description: >-
        Prespecified additive and multiplicative interaction estimates for each
        HLA or non-HLA risk allele and exposure class, including confidence
        intervals and independent-cohort replication.
      direction: THRESHOLD_DEPENDENT
      interpretation: >-
        Only a replicated interaction with exposure preceding disease
        prioritizes a specific host-exposure pair for the cellular experiment.
    - name: Incident granulomatous disease phenotype
      target: pathophysiology#Granuloma Formation
      description: >-
        Centrally adjudicated incident pulmonary sarcoidosis, organ pattern, and
        Löfgren versus non-Löfgren presentation and acute-resolving versus
        chronic or fibrotic course.
      direction: POSITIVE
    controls:
    - name: Exposed unaffected controls
      description: >-
        Participants with comparable measured exposure and ancestry who do not
        develop sarcoidosis, separating exposure from disease response.
    - name: Genetically matched unexposed controls
      description: >-
        Participants carrying the candidate allele without the candidate
        exposure, separating genotype from the interaction.
    - name: Negative-control exposure and allele pairs
      description: >-
        Prespecified unrelated exposures and alleles used to detect recall,
        occupational, ancestry, or multiple-testing artifacts.
    decision_criterion: >-
      The gene-environment arm is supported only when the same prespecified
      exposure-allele pair shows exposure-before-disease temporality, a
      corrected interaction effect beyond both main effects, a compatible
      dose-response, and directionally consistent replication. Main effects
      without interaction support only separate exposure and host-risk nodes.
      A well-powered null interaction across both cohorts would weaken that
      specific pair, not exclude other exposures, alleles, or non-genetic
      susceptibility.
    would_support:
    - mechanistic_hypothesis#environmental_exposure_host_susceptibility_trigger_model
  - experiment_id: exp_sarcoidosis_exposure_sensor_hla_causal_chain
    name: Exposure-matched sensor-to-HLA-to-CD4 pulmonary causal-chain assay
    description: >-
      For exposure-allele pairs that replicate epidemiologically, compare
      bronchoalveolar antigen-presenting cells and autologous CD4+ T cells from
      treatment-naive pulmonary-sarcoidosis cases, exposed unaffected controls,
      and allele-matched unexposed controls. Apply chemically and
      microbiologically characterized matched and mismatched exposure
      preparations in a short time course. Use orthogonal blockade or editing
      of response-nominated innate sensors and HLA class II, then measure early
      antigen-presenting-cell responses, HLA-bound peptides, antigen-specific
      TCR activation, Th1/Th17.1 polarization, and granuloma-like organization.
      Advance only exposure preparations that are endotoxin-controlled,
      noncytotoxic, and reproducible across donors.
    experiment_type:
      preferred_term: exposure-stratified pulmonary immune-cell perturbation assay
    model_systems:
    - name: Autologous alveolar antigen-presenting-cell and CD4+ T-cell coculture
      description: >-
        Bronchoalveolar macrophage or dendritic-cell preparations cocultured
        with autologous CD4+ T cells from cases and matched control groups.
      experimental_model_type: CO_CULTURE
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      tissue_term:
        preferred_term: lung
        term:
          id: UBERON:0002048
          label: lung
      cell_types:
      - preferred_term: alveolar macrophage
        term:
          id: CL:0000583
          label: alveolar macrophage
      - preferred_term: conventional dendritic cell
        term:
          id: CL:0000990
          label: conventional dendritic cell
      - preferred_term: CD4-positive helper T cell
        term:
          id: CL:0000492
          label: CD4-positive helper T cell
    perturbations:
    - name: Matched and mismatched exposure challenge
      target: environmental#Occupational Exposures
      description: >-
        Compare the epidemiologically matched exposure preparation with other
        exposure classes, vehicle, and dose-matched particle or bioaerosol
        controls.
      effect: exposure-class-specific challenge
    - name: Candidate innate-sensor loss or blockade
      target: pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
      description: >-
        Perturb only sensors nominated by an early reproducible response, using
        genetic and pharmacologic approaches with on-target rescue where
        feasible.
      effect: reduced candidate exposure sensing
    - name: HLA class II blockade
      target: pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
      description: >-
        Block the implicated HLA-DR or HLA-DP presentation step and compare it
        with isotype and irrelevant-HLA controls.
      effect: reduced HLA-restricted antigen presentation
    readouts:
    - name: Early antigen-presenting-cell response
      target: pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
      description: >-
        Time-resolved uptake, viability, sensor-proximal signaling, cytokines,
        costimulatory state, and HLA class II surface abundance before T-cell
        activation.
      direction: POSITIVE
    - name: Exposure-linked HLA immunopeptidome and TCR response
      target: pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
      description: >-
        Exposure-derived or exposure-modified-self HLA-bound peptides,
        peptide-specific tetramer responses, and activation of expanded
        granuloma-linked TCR clonotypes.
      direction: POSITIVE
    - name: CD4+ T-cell polarization
      target: pathophysiology#Th17.1 Polarization and IFN-gamma Production
      description: >-
        Antigen-specific IFN-gamma/IL-17A production, Th1/Th17.1 state, and Treg
        balance after matched versus mismatched challenge.
      direction: POSITIVE
    - name: Granuloma-like organization
      target: pathophysiology#Granuloma Formation
      description: >-
        Multicellular aggregate formation, macrophage epithelioid state, and
        spatial T-cell/macrophage organization distinguished from nonspecific
        toxicity or foreign-body aggregation.
      direction: POSITIVE
    controls:
    - name: Exposed unaffected donor cells
      description: >-
        Tests whether the candidate response is a generic consequence of
        exposure rather than a disease- or susceptibility-linked response.
    - name: Allele-matched unexposed donor cells
      description: Separates the candidate HLA background from prior exposure.
    - name: Endotoxin, viability, and generic-particle controls
      description: >-
        Exclude contaminant-driven innate activation, cytotoxicity, and
        nonspecific foreign-body aggregation.
    - name: Matched versus mismatched exposure and HLA controls
      description: >-
        Test the exposure and restriction-element specificity required by the
        hypothesis rather than generic immune hyperreactivity.
    - name: Granulomatous disease controls
      description: >-
        Include exposure-defined chronic beryllium disease, silicosis, and
        hypersensitivity pneumonitis samples where available to distinguish an
        idiopathic-sarcoidosis response from known exposure diseases or generic
        granulomatous inflammation.
    decision_criterion: >-
      A specific trigger chain is supported only if a replicated
      exposure-allele pair produces an early, noncytotoxic
      exposure-class-specific antigen-presenting-cell response; yields a
      defined HLA-bound antigen or modified-self peptide and cognate TCR
      activation; precedes CD4 polarization and granuloma-like organization;
      and loses those downstream readouts after orthogonal sensor and
      restriction-element perturbation. Generic inflammation, aggregation
      without antigen-specific T-cell activation, a response shared by exposed
      unaffected controls, or microbial-antigen responses independent of the
      recorded exposure would favor toxicity, foreign-body, or
      antigen-persistence alternatives. Failure after adequate target
      engagement weakens only the tested exposure-sensor-HLA chain.
    would_support:
    - mechanistic_hypothesis#environmental_exposure_host_susceptibility_trigger_model
    evidence:
    - reference: PMID:30134122
      reference_title: "IL-13-regulated Macrophage Polarization during Granuloma Formation in an In Vitro Human Sarcoidosis Model."
      supports: PARTIAL
      evidence_source: IN_VITRO
      snippet: >-
        Compared with identically treated PBMCs of control subjects (n = 5),
        purified protein derivative-treated sarcoidosis PBMCs (n = 6) were
        distinguished by the formation of cellular aggregates resembling
        granulomas.
      explanation: >-
        This small patient-cell study provides feasibility precedent for
        case-control antigen challenge and granuloma-like readouts, not evidence
        for a particular environmental exposure in vivo.
  evidence:
  - reference: PMID:42471775
    reference_title: "Current understanding of environmental exposures and sarcoidosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Several environmental exposures are associated with a risk for
      sarcoidosis, but their exact role is incompletely understood.
    explanation: >-
      The source review states the unresolved causal role that defines this
      knowledge gap.
  - reference: PMID:15347561
    reference_title: "A case control etiologic study of sarcoidosis: environmental and occupational risk factors."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The study did not identify a single, predominant cause of sarcoidosis. We
      identified several exposures associated with sarcoidosis risk, including
      insecticides, agricultural employment, and microbial bioaerosols.
    explanation: >-
      The primary ACCESS study supplies exposure-class associations while
      explicitly failing to identify one cause or a mechanistic chain.
  - reference: PMID:19382531
    reference_title: "HLA and environmental interactions in sarcoidosis."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Significant interaction was observed between HLA DRB1*1101 and
      insecticide exposure at work (p < 0.10) and suggestive interaction was
      observed between HLA DRB1*1101 and exposure to mold and musty odors and
      DRB1*1501 and insecticide exposure at work (P < 0.15).
    explanation: >-
      These exploratory interaction thresholds motivate preregistered
      replication but are insufficient for a causal exposure-allele edge.
  - reference: PMID:25305207
    reference_title: "Genetic susceptibility to beryllium: a case-referent study of men and women of working age with sarcoidosis or other chronic lung disease."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      No increase in sarcoidosis was seen with either Glu69 or beryllium
      exposure (none, <10, ≥10 years) as main effects: longer duration in
      possible beryllium jobs was related to COPD. In Glu69 positive men with
      exposure ≥10 years, the trend towards increasing rate of COPD was
      reversed, and a significant interaction of duration of exposure and Glu69
      was detected (OR=4.51 95% CI 1.17 to 17.48).
    explanation: >-
      The main-effect nulls plus the duration-by-Glu69 interaction point to
      possible chronic beryllium disease misclassified as sarcoidosis and
      justify exposure history and beryllium lymphocyte proliferation testing.
      They neither validate the idiopathic trigger model nor broadly refute
      gene-environment interaction.
  - reference: PMID:31126090
    reference_title: "Genetic Variants Associated with FDNY WTC-Related Sarcoidosis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In our secondary analysis, we did not find statistical evidence of an
      interaction between common variants and the degree of WTC exposure.
    explanation: >-
      The null result constrains a dose-dependent WTC gene-exposure interaction
      and requires candidate pairs to replicate in adequately powered cohorts.
  - reference: PMID:20813038
    reference_title: "No evidence of altered alveolar macrophage polarization, but reduced expression of TLR2, in bronchoalveolar lavage cells in sarcoidosis."
    supports: REFUTE
    evidence_source: IN_VITRO
    snippet: >-
      Overall, there was no evidence for alveolar macrophage polarization in
      sarcoidosis. However, there was a reduced TLR2 mRNA expression in patients
      with Löfgren's syndrome, which may be of relevance for macrophage
      interactions with a postulated sarcoidosis pathogen, and for the
      characteristics of the ensuing T cell response.
    explanation: >-
      These bronchoalveolar observations constrain a uniform macrophage
      polarization or TLR2-expression account. They do not exclude other PRRs
      or an exposure-specific sensing program and therefore do not justify a
      TLR2 trigger edge.
- discussion_id: gap_sarcoidosis_immunologic_paradox_anergy_vs_activation
  prompt: >-
    Why does sarcoidosis combine vigorous compartmentalized granulomatous CD4+
    Th1/Th17.1 activity at disease sites with peripheral T-cell lymphopenia,
    anergy, and PD-1+ exhaustion, and would restoring exhausted T-cell function
    promote resolution or instead intensify granulomatous inflammation?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
  - pathophysiology#Th17.1 Polarization and IFN-gamma Production
  rationale: >-
    Sarcoidosis presents a long-standing immunologic paradox: an exaggerated,
    IFN-gamma-rich local granulomatous CD4+ T-cell response coexists with
    systemic hyporesponsiveness - cutaneous anergy, peripheral CD4+ lymphopenia,
    reduced proliferation on TCR stimulation, and PD-1+ exhaustion markers. This
    matters therapeutically and is directionally unresolved: CD4+ T-cell
    exhaustion reverses in patients who spontaneously remit (suggesting
    exhaustion tracks with, and may even favor, resolution), yet
    checkpoint-inhibitor cancer therapy that reverses T-cell exhaustion can
    precipitate sarcoid-like granulomatous reactions. Whether checkpoint
    restoration would clear persistent antigen and resolve disease or instead
    reignite granuloma formation is unknown, and the entry's antigen/T-cell
    nodes do not currently capture this exhaustion axis.
  proposed_experiments:
  - experiment_id: exp_sarcoidosis_tcell_exhaustion_resolution_tracking
    name: Longitudinal T-cell exhaustion versus resolution tracking with ex vivo checkpoint modulation
    description: >-
      In newly diagnosed sarcoidosis patients, serially phenotype paired
      peripheral-blood and bronchoalveolar-lavage CD4+ T cells for exhaustion
      (PD-1, TIM-3, LAG-3), proliferative capacity, Th1/Th17.1 cytokine output,
      and apoptosis, stratifying by subsequent spontaneous resolution versus
      chronic/progressive course. In parallel, apply ex vivo PD-1/PD-L1 blockade
      to patient-derived cells and PBMC granuloma-in-a-dish models to test
      whether reversing exhaustion enhances antigen clearance or amplifies
      granuloma formation.
    experiment_type:
      preferred_term: longitudinal immunophenotyping with ex vivo checkpoint perturbation
    model_systems:
    - name: Paired blood and BAL CD4+ T cells with PBMC granuloma model
      description: >-
        Serial peripheral-blood and bronchoalveolar-lavage CD4+ T cells from
        remitting and chronic sarcoidosis patients, plus autologous PBMC-derived
        granuloma-in-a-dish cultures for checkpoint-modulation readouts.
      experimental_model_type: PRIMARY_CELL_CULTURE
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      tissue_term:
        preferred_term: lung
        term:
          id: UBERON:0002048
          label: lung
      cell_types:
      - preferred_term: CD4-positive helper T cell
        term:
          id: CL:0000492
          label: CD4-positive helper T cell
    readouts:
    - name: T-cell exhaustion trajectory versus clinical course
      target: pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
      description: >-
        PD-1/TIM-3/LAG-3 expression, proliferative capacity, and apoptosis over
        time, compared between patients who spontaneously resolve and those who
        progress.
    - name: Effect of checkpoint blockade on granuloma output
      target: pathophysiology#Th17.1 Polarization and IFN-gamma Production
      description: >-
        Change in Th17.1/IFN-gamma output and granuloma-like aggregate
        formation after ex vivo PD-1/PD-L1 blockade, to determine whether
        exhaustion reversal favors resolution or amplifies granulomatous
        inflammation.
    decision_criterion: >-
      The exhaustion axis would be clarified if spontaneous resolvers show
      reversal of the exhaustion phenotype with restored antigen clearance,
      while ex vivo checkpoint blockade in chronic-disease cells amplifies
      Th17.1/IFN-gamma output and granuloma formation - indicating exhaustion is
      a brake whose removal is pathogenic rather than therapeutic in established
      disease.
  evidence:
  - reference: PMID:29234685
    reference_title: "Local and Systemic CD4(+) T Cell Exhaustion Reverses with Clinical Resolution of Pulmonary Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "sarcoidosis CD4+ T cells demonstrated reductions in Th1 cytokine expression, proliferative capacity (p < 0.05), enhanced apoptosis (p < 0.01), and increased PD-1 expression (p < 0.001)."
    explanation: >
      Quantifies the peripheral/systemic arm of the paradox - reduced
      proliferation, cytokine output, and increased PD-1 exhaustion markers on
      sarcoidosis CD4+ T cells despite active granulomatous disease.
  - reference: PMID:29234685
    reference_title: "Local and Systemic CD4(+) T Cell Exhaustion Reverses with Clinical Resolution of Pulmonary Sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Reversal of CD4+ T cell exhaustion was observed in subjects undergoing spontaneous resolution"
    explanation: >
      Directly links reversal of the exhaustion phenotype to spontaneous
      clinical resolution, framing the central unresolved directional question
      of whether exhaustion is protective or pathogenic.
- discussion_id: gap_sarcoidosis_dr3_antigen_identity_and_resolution_paradox
  prompt: >-
    Is the disease-defining sarcoidosis antigen self (vimentin) or foreign
    (mycobacterial mKatG), or is there no true dichotomy because one
    HLA-DRB1*03-restricted public TCR recognizes several antigens - and why does
    HLA-DRB1*03, the allele anchoring the antigen-specific response, predict
    spontaneous resolution rather than chronic disease?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
  rationale: >-
    A 2026 OpenScientist hypothesis-search of the vimentin_autoimmunity_model
    surfaced two coupled unknowns. First, the antigen identity is unresolved and
    the self-versus-foreign framing may be false: the DR3+ sarcoid lung presents
    a milieu of antigens, but only the vimentin T-cell response is demonstrably
    HLA-DRB1*03-restricted, whereas responses to ATP synthase and lysyl-tRNA
    synthetase also occur in DR3-negative patients and the microbial antigen
    mKatG is documented as a tissue antigen whose relationship to the
    Valpha2.3/Vbeta22 repertoire has not been directly tested. Whether these
    antigens converge on the same public clone is unknown, and the
    molecular-mimicry bridge that would unify self and foreign is unsupported at
    the linear-sequence level. Second, and paradoxically,
    HLA-DRB1*03 - the allele that anchors this antigen-specific response - is a
    dominant good-prognosis allele predicting spontaneous resolution, which is
    hard to reconcile with classic self-perpetuating autoimmunity and instead
    favors an antigen-recognition-coupled-to-effective-clearance model. Resolving
    the antigen identity and the resolution paradox would determine whether the
    DR3-restricted response is a driver to be suppressed or a clearance program to
    be supported.
  proposed_experiments:
  - experiment_id: exp_sarcoidosis_dr3_tetramer_antigen_ranking
    name: HLA-DR3 tetramer multi-antigen ranking against clinical course
    description: >-
      In HLA-DRB1*03+ patients stratified by Lofgren/resolving versus
      non-resolving course (and DR3+ healthy controls), quantify the frequency
      and avidity of CD4+ T cells binding HLA-DR3 tetramers loaded in parallel
      with vimentin (Vim429-443), ATP synthase, lysyl-tRNA synthetase, and mKatG
      peptides, using paired bronchoalveolar-lavage and blood samples, and relate
      antigen-specific frequencies to spontaneous resolution versus progression.
    experiment_type:
      preferred_term: HLA class II tetramer antigen-ranking study
    model_systems:
    - name: HLA-DRB1*03+ sarcoidosis BAL and blood CD4+ T cells
      description: >-
        Paired bronchoalveolar-lavage and peripheral-blood CD4+ T cells from
        HLA-DRB1*03+ resolving and non-resolving sarcoidosis patients and DR3+
        controls, interrogated with a panel of DR3 peptide tetramers.
      experimental_model_type: PRIMARY_CELL_CULTURE
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      tissue_term:
        preferred_term: lung
        term:
          id: UBERON:0002048
          label: lung
      cell_types:
      - preferred_term: CD4-positive helper T cell
        term:
          id: CL:0000492
          label: CD4-positive helper T cell
    readouts:
    - name: Antigen-specific tetramer frequency versus disease course
      target: pathophysiology#Antigen Recognition and CD4+ T-Cell Activation
      description: >-
        Relative frequency and avidity of vimentin-, ATP-synthase-,
        lysyl-tRNA-synthetase-, and mKatG-tetramer+ CD4+ T cells, compared between resolving
        and non-resolving DR3+ patients, testing whether any single antigen
        dominates and whether antigen-reactivity tracks with resolution.
    decision_criterion: >-
      The single-antigen vimentin model would be supported if vimentin-tetramer+
      cells dominate and predict outcome; the shared multi-antigen program would
      be supported if several antigens engage the restricted TCR at comparable
      frequency; and the clearance reframing would be supported if higher
      antigen-specific frequencies track with spontaneous resolution rather than
      progression.
  evidence:
  - reference: PMID:19786367
    reference_title: "Autoimmune T cell responses to antigenic peptides presented by bronchoalveolar lavage cell HLA-DR molecules in sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "BAL T cell responses against peptides derived from ATP synthase or from lysyl-tRNA synthetase were detected in DRB10301(pos) as well as DRB10301(neg) patients"
    explanation: >
      Documents multiple HLA-DR-presented antigens beyond vimentin, motivating
      the shared multi-antigen framing over a single disease-defining antigen.
  - reference: PMID:15753209
    reference_title: "Mycobacterial catalase-peroxidase is a tissue antigen and target of the adaptive immune response in systemic sarcoidosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "suggesting that remnant mycobacterial catalase-peroxidase is one target of the adaptive immune response driving granulomatous inflammation in sarcoidosis"
    explanation: >
      Establishes a microbial antigen (mKatG) as a competing target of the same
      adaptive response, the foreign-antigen pole of the unresolved antigen-identity
      question.
  - reference: PMID:20187937
    reference_title: "Different HLA-DRB1 allele distributions in distinct clinical subgroups of sarcoidosis patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "DRB1*07, DRB1*14 and DRB1*15 generally associated with, while DRB1*01 and DRB1*03 protected against, a non-resolving disease"
    explanation: >
      Quantifies the resolution paradox: DR3 protects against non-resolving
      disease, the observation the proposed experiment is designed to reconcile
      with an antigen-specific mechanism.
- discussion_id: gap_sarcoidosis_vimentin_mouse_model_translational_validity
  prompt: >-
    Does the vimentin-immunization-plus-vimentin-bead mouse granuloma model
    reflect the mechanism of spontaneous human sarcoidosis, or does forced
    immunization and particulate bead challenge bypass the (unknown) natural
    initiating events - i.e., is vimentin a genuine initiating autoantigen in
    humans or only sufficient to drive granulomas once immunity is artificially
    established?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Self-Antigen Vimentin Presentation by HLA-DRB1*03
  - pathophysiology#Granuloma Formation
  rationale: >-
    PMID:35434591 is the only causal (rather than associative) support for the
    vimentin autoimmunity model: vimentin-immunized mice challenged with
    vimentin-coated beads develop sarcoid-like Th1/Th17 lung granulomas. This is
    genuine mechanistic evidence that anti-vimentin immunity is sufficient to
    produce sarcoid-like pathology, but its translational validity is uncertain -
    the model requires deliberate immunization against vimentin plus an
    intravenous particulate (bead) challenge, neither of which is a documented
    step in spontaneous human disease, and the model also engaged ILC2/TH2
    programs not central to human sarcoid granulomas. Per the KB convention this
    is a HUMAN_MODEL_MISMATCH (model evidence exists; human translational
    validity is the open question), not a generic knowledge gap: the question is
    not whether vimentin autoimmunity can cause granulomas but whether it
    initiates them in humans.
  proposed_experiments:
  - experiment_id: exp_sarcoidosis_vimentin_natural_initiation_test
    name: Test for spontaneous anti-vimentin priming preceding human sarcoidosis
    description: >-
      In pre-symptomatic or incident human cohorts (e.g. HLA-DRB1*03+
      individuals, or biobank samples predating diagnosis), determine whether
      anti-vimentin T-/B-cell responses and Valpha2.3/Vbeta22 clonal expansion
      arise before clinical granulomatous disease and without an obvious
      immunizing event, and whether they track antigen exposure. In parallel,
      develop a spontaneous (non-immunization, non-bead) model or ex vivo human
      granuloma-in-a-dish system to test whether endogenously processed vimentin
      is sufficient to nucleate granuloma formation.
    experiment_type:
      preferred_term: pre-symptomatic cohort plus spontaneous-model translational test
    model_systems:
    - name: Pre-diagnosis human cohort and non-immunization granuloma model
      description: >-
        Incident/pre-symptomatic HLA-DRB1*03+ human samples paired with a
        spontaneous or ex vivo human granuloma model that does not rely on forced
        vimentin immunization or particulate bead challenge.
      experimental_model_type: PRIMARY_CELL_CULTURE
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      tissue_term:
        preferred_term: lung
        term:
          id: UBERON:0002048
          label: lung
      cell_types:
      - preferred_term: CD4-positive helper T cell
        term:
          id: CL:0000492
          label: CD4-positive helper T cell
    readouts:
    - name: Temporal order of anti-vimentin immunity versus disease onset
      target: pathophysiology#Self-Antigen Vimentin Presentation by HLA-DRB1*03
      description: >-
        Whether anti-vimentin T-/B-cell reactivity and Valpha2.3/Vbeta22 clonal
        expansion precede clinical granulomatous disease in humans without a
        deliberate immunizing event.
    decision_criterion: >-
      The mouse model's translational validity would be supported if
      anti-vimentin immunity and the restricted clone arise spontaneously before
      human disease onset and endogenous vimentin nucleates granulomas without
      artificial immunization/bead challenge; it would be undercut if
      anti-vimentin responses are only a downstream consequence of established
      granulomatous tissue damage.
  evidence:
  - reference: PMID:35434591
    reference_title: "Systemic immune response to vimentin and granuloma formation in a model of pulmonary sarcoidosis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Vimentin-immunized mice developed lung granulomas following intravenous challenge with vimentin-coated beads."
    explanation: >
      The causal mouse result whose translational validity to spontaneous human
      sarcoidosis this HUMAN_MODEL_MISMATCH discussion frames as the open
      question - it requires deliberate immunization and bead challenge.
datasets:

📚

References & Deep Research

Deep Research

Claude Code ▸

1. Disease Information

claude-haiku-4-5-20251001, claude-opus-4-8[1m] 24 citations 2026-06-24T15:27:05.909799

1. Disease Information

Overview. Sarcoidosis is a multisystem granulomatous inflammatory disease of unknown cause, characterized by the formation of non-caseating (non-necrotizing) epithelioid-cell granulomas in affected organs — most commonly the lungs and intrathoracic lymph nodes (>90% of patients), but potentially almost any organ. It results from an exaggerated immune response, in genetically susceptible individuals, to one or more poorly defined antigens. Disease behavior ranges from asymptomatic and spontaneously resolving (e.g., Löfgren syndrome) to chronic, progressive, fibrotic, and occasionally fatal.

"Sarcoidosis is an inflammatory disease of unknown cause involving the formation of granulomas in almost any organ, although typically in the lungs." — Grunewald et al., Nat Rev Dis Primers 2019 (article)

Key identifiers: | Resource | ID | |---|---| | MONDO | MONDO:0019338 (sarcoidosis) — verify with runoak -i sqlite:obo:mondo info MONDO:0019338 | | OMIM | 181000 (SARCOIDOSIS, SS1 / susceptibility) | | Orphanet | ORPHA:797 (Sarcoidosis) | | ICD-10 | D86 (D86.0 pulmonary; D86.2 lung w/ lymph nodes; D86.3 skin; D86.8x specified sites; D86.9 unspecified) | | ICD-11 | 4B20 (Sarcoidosis) | | MeSH | D012507 (Sarcoidosis) | | DOID | DOID:11335 | | UMLS | C0036202 |

Synonyms / alternative names: Besnier-Boeck-Schaumann disease; Boeck sarcoid; Boeck disease; Schaumann disease; benign lymphogranulomatosis; sarcoid; (historical) "lupus pernio" refers specifically to the chronic cutaneous facial form.

Data derivation: Information here is aggregated disease-level knowledge (society guidelines, registries, GWAS meta-analyses, cohort studies) rather than individual EHR records. Major cohorts referenced: ACCESS (A Case Control Etiologic Study of Sarcoidosis, US, n=736), GRADS, WASOG registry, Swedish national registers, and the DZL/GenPhenReSa European cohort.

2. Etiology

Disease causal factors. Sarcoidosis is a complex (multifactorial) disease: a combination of genetic susceptibility + environmental/microbial antigen exposure → dysregulated immune granulomatous response. No single cause is established. The leading paradigm is an antigen-driven, Th1/Th17-polarized immune reaction.

Candidate antigenic triggers (all unproven as causal): - Microbial: Mycobacterium tuberculosis-derived proteins (notably mKatG, catalase-peroxidase) and ESAT-6; Cutibacterium (Propionibacterium) acnes — the only microorganism repeatedly isolated from sarcoid granulomas, especially in Japanese cohorts. (NCBITaxon:1747 Cutibacterium acnes; NCBITaxon:1773 M. tuberculosis.) These are thought to act as persistent poorly degradable antigens rather than active infection. - Environmental/occupational: insecticides, mold/musty odors, agricultural employment, and inorganic particulates. The strongest occupational signal is the WTC (World Trade Center) dust "sarcoidosis-like granulomatous disease" among first responders. - Autoimmune component: increasing evidence of autoantigen recognition (e.g., vimentin presented by HLA-DRB1*03).

Risk factors — genetic (see §4): HLA class II (HLA-DRB1, HLA-DQB1) is the dominant locus; non-HLA loci include BTNL2, ANXA11, NOTCH4, IL23R, RAB23, OS9, IL12B, FAM177B, C-C chemokine genes.

Risk factors — environmental/demographic: - Race/ancestry: African ancestry → higher incidence and severity (see §9). - Family history: first-degree relatives have a ~3.7–5× increased risk (ACCESS study; sibling relative risk highest). - Sex: roughly equal; female peak slightly later. - Occupational/inhalational exposures (above); firefighting/WTC.

Protective factors: - Smoking is paradoxically inversely associated with sarcoidosis risk (one of the few granulomatous/ILD conditions where smoking appears protective) — though it may worsen some outcomes. ⚠ verify. - Genetic: HLA-DRB101 and HLA-DRB104 are associated with reduced risk; DRB1*03:01 (DR3) is strongly associated with the self-limiting, good-prognosis Löfgren phenotype (acts as a prognostic protective allele, not a susceptibility-reducing one).

Gene–environment interactions: HLA-DRB103-restricted T-cell responses to specific antigens (e.g., vimentin) define the Löfgren-syndrome resolving phenotype — a paradigmatic GxE/GxImmunogenetic interaction. C. acnes*-reactive responses are modulated by HLA background (CTD/PheGenI candidate area).

3. Phenotypes

Sarcoidosis is defined by organ-specific granulomatous involvement plus constitutional features. Approximate frequencies (ACCESS, WASOG, GenPhenReSa cohorts):

Phenotype	HPO term (suggested)	Approx. frequency	Notes
Intrathoracic/pulmonary involvement	HP:0002088 (Abnormal lung morphology) / HP:0006515 (Interstitial pulmonary abnormality)	>90%	Defining feature
Bilateral hilar lymphadenopathy	HP:0012246 (hilar lymphadenopathy) / HP:0002721 (Immunodeficiency? no) — use HP:0030075 (Abnormal mediastinal morphology)	~majority on imaging	Scadding stage I
Dyspnea	HP:0002094 (Dyspnea)	~30–50%
Cough (chronic, dry)	HP:0031246 (Chronic cough) / HP:0012735 (Cough)	common
Fatigue	HP:0012378 (Fatigue)	up to ~50–70%	major QoL driver
Erythema nodosum	HP:0012219 (Erythema nodosum)	~10–25% (higher in N. Europeans)	part of Löfgren syndrome
Lupus pernio / other skin lesions	HP:0000962 (Hyperkeratosis)? better: HP:0011123 (Inflammatory abnormality of the skin)	skin ~25–30% overall	lupus pernio = chronic marker
Uveitis / ocular	HP:0000554 (Uveitis)	ocular ~10–25%	anterior > posterior
Peripheral lymphadenopathy	HP:0002716 (Lymphadenopathy)	~10–15%
Hepatic granulomas	HP:0001392 (Abnormal liver morphology) / HP:0002240 (Hepatomegaly)	~10–20% (often subclinical)
Splenomegaly	HP:0001744 (Splenomegaly)	~5–10%
Arthralgia/arthritis	HP:0002829 (Arthralgia) / HP:0001369 (Arthritis)	acute (Löfgren) common
Cardiac sarcoidosis	HP:0001638 (Cardiomyopathy) / HP:0011675 (Arrhythmia) / HP:0001712 (Left ventricular hypertrophy)?	clinically ~5%; subclinical up to ~25%	leading cause of death (esp. Japan)
Neurosarcoidosis	HP:0002383 (Encephalitis)? better HP:0000759 (Abnormal peripheral nervous system) / HP:0100256 (Cranial nerve VII palsy → HP:0010628 Facial palsy)	~5–10%	facial nerve palsy classic
Hypercalcemia	HP:0003072 (Hypercalcemia)	~5–10%	from 1,25-(OH)₂-vit D₃ overproduction
Hypercalciuria / nephrolithiasis	HP:0002150 (Hypercalciuria) / HP:0000787 (Nephrolithiasis)	hypercalciuria ~up to 40%
Renal (granulomatous interstitial nephritis)	HP:0000124 (Renal tubular dysfunction)/HP:0000790	uncommon
Small-fiber neuropathy	HP:0000763 (Sensory neuropathy)	underrecognized, common	autonomic + sensory sx
Parotid/salivary (with uveitis+fever = Heerfordt syndrome)	HP:0010286 (Parotitis)?	rare	uveoparotid fever

Onset & severity: Adult-onset (peak 25–45y; second female peak >50y). Severity variable; ~50–70% remit (often spontaneously), ~10–30% develop chronic/progressive disease, and ~5–10% develop pulmonary fibrosis. Quality-of-life impact is substantial and often disproportionate to organ burden — driven by fatigue, dyspnea, depression, and small-fiber neuropathy; measured by the disease-specific King's Sarcoidosis Questionnaire (KSQ) and SF-36/FAS (Fatigue Assessment Scale).

4. Genetic / Molecular Information

Sarcoidosis is polygenic with no monogenic causal gene; OMIM lists multiple susceptibility loci (SS1–SS6).

Major susceptibility loci (germline; all common variants, not "pathogenic" in ACMG Mendelian sense):

Gene	HGNC	Locus	Key variant / finding	Evidence
HLA-DRB1	hgnc:4948	6p21 (MHC II)	DRB111:01 ↑risk (both Black & White); 03:01 → Löfgren/resolving; 14,15 → chronic; 01,*04 protective	GWAS, replicated
BTNL2	hgnc:1142	6p21	rs2076530 G→A truncating splice variant ↑risk (OR ~1.6–1.8)	⚠ PMID for Valentonyte 2005 Nat Genet
ANXA11	hgnc:535	10q22	rs1049550 (R230C) — annexin A11, apoptosis regulation	confirmed German/Czech/Portuguese/US (Nature Genes Immun)
NOTCH4	hgnc:7884	6p21	eQTL/GWAS, innate immunity	PMID 38390497 ⚠
IL23R	hgnc:19100	1p31	Th17 axis
RAB23, OS9, IL12B, FAM177B, SH2B3/ATXN2	—	various	GWAS hits

eQTL study (2024): "Examination of eQTL Polymorphisms Associated with Increased Risk of Progressive Complicated Sarcoidosis in European and African Descent Subjects" — implicates innate immunity, MHC class II, and allograft-rejection pathways (PMID 38390497 ⚠).

Clinical-course associations: ANXA11 rs1049550 C/T, BTNL2 rs2076530 G/A, and HLA class I/II alleles modulate disease course (PMID 27662826 ✓, Morais 2018 Clin Respir J).

Variant classification note: These are susceptibility/risk alleles, not Mendelian pathogenic variants — for the dismech entry, model them as GENO susceptibility associations, not causal pathogenic variants. Allele frequencies are common (MAF often 0.1–0.4 in gnomAD); origin is germline; functional consequence is largely altered antigen presentation (HLA), altered immune signaling (BTNL2 = loss of negative T-cell costimulation; ANXA11 = apoptosis modulation).

Somatic/acquired: A key recent insight is acquired mTORC1 pathway activation in granuloma macrophages (see §6) — i.e., a somatic/functional signaling lesion, not inherited.

Modifier genes: TNF-α promoter polymorphisms (−308A) and HLA alleles modify severity/Löfgren prognosis. Epigenetics: altered DNA methylation and miRNA profiles reported in BAL cells and granulomas (DiseaseMeth/GEO candidate area); not yet definitively mechanistic. No characteristic chromosomal abnormality.

5. Environmental Information

Environmental/occupational factors (CTD/ACCESS): agricultural/musty/mold environments, insecticides, metal/silica dust, WTC dust (granulomatous "sarcoid-like" disease in responders); firefighting; possibly photocopier toner. Beryllium exposure causes chronic beryllium disease (berylliosis) — a clinically/histologically near-identical mimic that must be excluded (BeLPT test).
Lifestyle: Smoking is inversely associated with risk (protective signal). Diet/obesity links weak.
Infectious agents (trigger candidates, not established pathogens): Cutibacterium acnes (NCBITaxon:1747), Mycobacterium tuberculosis antigens mKatG/ESAT-6 (NCBITaxon:1773). The "latent microbial reactivation + immune dysregulation" model is reviewed in 2025 work (PMC12362391). Sarcoidosis is not contagious.

6. Mechanism / Pathophysiology

Core causal chain (upstream → downstream):

Antigen exposure (microbial/environmental/auto-) in a genetically susceptible host →
Antigen presentation by APCs (dendritic cells, macrophages) via HLA class II to CD4⁺ T cells →
Th1 / Th17.1 polarization with IFN-γ, IL-2, TNF-α, IL-12, IL-18, IL-23 production; oligoclonal T-cell expansion (BAL CD4:CD8 ratio often >3.5) →
Macrophage activation and epithelioid/multinucleated giant cell differentiation → non-caseating granuloma formation; macrophages secrete ACE and 1α-hydroxylase (→ hypercalcemia) →
Granuloma maintenance by persistent antigen + cytokines →
Either resolution (Treg-mediated) or M2-macrophage / TGF-β-driven fibrosis → irreversible organ damage.

Key molecular pathways (suggested GO/KEGG): - mTORC1 / PI3K-AKT-mTOR — landmark mechanism. Macrophage-specific Tsc2 deletion → constitutive mTORC1 activation → CDK4-driven proliferation → spontaneous granulomas in mice, and mTORC1 activity marks progressive human disease (Linke et al., Nat Immunol 2017; PMID 28092373 ✓ / DOI 10.1038/ni.3655). GO:0031929 (TOR signaling). A 2023 mTORC1-dependent cardiac sarcoidosis mouse model extends this (PMID 37750561 ✓). - JAK–STAT (IFN-γ / STAT1) — drives the granuloma transcriptome; targetable (tofacitinib normalizes it — see §12). GO:0007259. - TNF-α / NF-κB — central to granuloma integrity; basis for anti-TNF therapy. GO:0033209. - NLRP3 inflammasome / IL-1β — innate amplification. Simultaneous mTORC1/JAK-STAT/NLRP3 activation documented in patients (PMC10454122). - CCL24–CCR3 axis (mTORC1-dependent) controls granuloma formation/maintenance (PMC12338499 ⚠ 2025).

"Activation of the metabolic checkpoint kinase mTORC1 in macrophages by deletion of the gene encoding tuberous sclerosis 2 (Tsc2) was sufficient to induce … excessive granuloma formation in vivo." — Linke et al. 2017

Cellular processes & cell types (suggested CL): CD4⁺ T helper cell CL:0000492, Th17 cell CL:0000899, regulatory T cell CL:0000815, macrophage CL:0000235, epithelioid cell / multinucleated giant cell, dendritic cell CL:0000451. Treg dysfunction is restored experimentally by IL-33 via PI3K/Akt/mTOR and TGF-β/Smad inhibition.

Immune involvement: Paradoxical state — heightened local (granuloma) Th1/Th17 activity but peripheral anergy/lymphopenia and T-cell exhaustion (PD-1↑); increasingly framed as having an autoimmune component. "Sarcoidosis pathogenesis reflects dysregulated crosstalk between innate and adaptive immunity … sustained by persistent antigen presentation to T cells" (Immunopathogenesis review, J Autoimmun 2024).

Tissue damage: chronic inflammation → fibrosis (TGF-β, M2 macrophages) — links to the dismech fibrotic_response module for pulmonary fibrosis; granuloma-driven destruction of cardiac conduction tissue, optic/cranial nerves.

Biochemical hallmarks: macrophage ACE overproduction; 1α-hydroxylase (CYP27B1)-mediated extrarenal calcitriol synthesis → hypercalcemia/hypercalciuria; elevated soluble IL-2 receptor (sIL-2R), chitotriosidase, neopterin.

Comprehensive mechanism reviews: Sarcoidosis: molecular mechanisms and therapeutic strategies (PMC11794924 ✓ 2025); Advance in pathogenesis of sarcoidosis (PMC10938127 2024).

7. Anatomical Structures Affected

Primary organs: lung UBERON:0002048, intrathoracic/hilar & mediastinal lymph nodes UBERON:0000029. Body system: respiratory system UBERON:0001004.
Secondary / multi-organ: skin UBERON:0002097; eye UBERON:0000970; heart UBERON:0000948 (myocardium UBERON:0002349, conduction system); CNS/peripheral nerves (brain UBERON:0000955; cranial nerve VII / facial nerve UBERON:0001647); liver UBERON:0002107; spleen UBERON:0002106; kidney UBERON:0002113; bone/bone marrow; parotid gland UBERON:0001831; joints.
Tissue/cell level: alveolar macrophages, epithelioid histiocytes, multinucleated giant cells (Langhans type), CD4⁺ lymphocytes; granulomas are typically perilymphatic in lung (bronchovascular bundles, septa, pleura — basis for transbronchial/EBUS yield).
Subcellular (GO Cellular Component): within macrophages — asteroid bodies and Schaumann bodies (calcified inclusions) are characteristic histologic inclusions; lysosomal/phagosomal compartments (GO:0005764).
Localization/laterality: pulmonary involvement is bilateral (bilateral hilar lymphadenopathy is the imaging signature); skin/eye often bilateral/symmetric.

8. Temporal Development

Onset: typically adult (20–45y), with a second peak in women >50y; pediatric sarcoidosis rare (early-onset Blau syndrome / NOD2 is a distinct Mendelian granulomatous mimic — do not conflate). Onset acute (Löfgren) or insidious.
Scadding chest-radiograph stages (prognostic): Stage 0 (normal) → I (bilateral hilar adenopathy) → II (adenopathy + parenchymal infiltrates) → III (parenchymal infiltrates alone) → IV (fibrosis/honeycombing). Higher stage → lower spontaneous remission.
Course patterns: self-limiting/remitting (~50–70%, often within 2–3 yrs), chronic-persistent, relapsing-remitting, or progressive-fibrotic. Löfgren syndrome (acute triad: bilateral hilar adenopathy + erythema nodosum + arthralgia/fever) has >85–90% spontaneous resolution, especially with HLA-DRB1*03.
Critical windows: treatment decisions typically deferred in asymptomatic Stage I; intervention prioritized for threatened vital-organ function (cardiac, neuro, ocular, progressive pulmonary).

9. Inheritance and Population

Epidemiology: - Incidence: ~1–15 per 100,000/yr, region-dependent — lowest in East Asia (~0.5–1), intermediate in N. America/Australia (~5–10), highest in Scandinavia (~11–15) (Rossides et al., J Intern Med 2023, DOI 10.1111/joim.13629). - Prevalence: roughly 1–40 per 100,000 (population-dependent); US lifetime risk ~2.4% (Black) vs ~0.85% (White). - Race: In the US, Black > White ~3–4:1; highest age-specific incidence in Black women aged 30–39 (~107/100,000) (Sarcoidosis Epidemiology: Race Matters, PMC7522309). Black patients have more multiorgan disease, more severe pulmonary disease, higher hospitalization and mortality. - Sex: approximately equal (slight female predominance); female onset peaks later. - Age: classic peak 25–45y; rising incidence in older adults (>65y); mean diagnosis age now >50 in some datasets.

Inheritance: Not Mendelian — complex/polygenic with environmental contribution. Familial clustering exists: ACCESS found first-degree relatives at ~5× risk (sibling relative risk highest); concordance higher in monozygotic twins. No classic penetrance/expressivity/anticipation/founder figures apply in the Mendelian sense. (For dismech: model inheritance as multifactorial/polygenic, GENO susceptibility, not AD/AR.)

England population-based study (2024) provides recent incidence/prevalence/mortality figures (PMC12002749); Japan nationwide claims study (PMC12127000).

10. Diagnostics

Diagnosis is one of exclusion + compatible clinico-radiologic picture + histologic non-caseating granulomas with no alternative cause (per ATS 2020 guideline, Crouser et al., Am J Respir Crit Care Med 2020;201(8):e26–e51; PMID 32293205 ✓).

Histopathology (gold standard, SNOMED/path): non-necrotizing (non-caseating) epithelioid-cell granulomas; Langhans giant cells; asteroid & Schaumann bodies; must exclude infection (special stains for AFB/fungi) and beryllium.

Tissue acquisition: EBUS-TBNA (endobronchial ultrasound–guided transbronchial needle aspiration) of mediastinal nodes is now first-line (higher yield, ATS-recommended); transbronchial lung biopsy; skin/peripheral node biopsy when accessible.

Biomarkers (supportive, not diagnostic alone): - Serum ACE — sensitivity ~62%, specificity ~76%. - Soluble IL-2 receptor (sIL-2R) — superior to ACE (sens ~88%, spec ~85%) (PMC6797090); also activity marker. - Hypercalcemia/hypercalciuria; chitotriosidase; lysozyme; neopterin. BAL CD4:CD8 ratio >3.5 supports diagnosis (high specificity). - LOINC: ACE LOINC:2004-6 ⚠; serum calcium LOINC:17861-6.

Imaging: - Chest radiograph (Scadding staging) and HRCT (perilymphatic micronodules, beaded fissures, hilar/mediastinal adenopathy). - ¹⁸F-FDG-PET/CT — disease activity, occult sites, viable inflammation vs fibrosis. - Cardiac MRI (late gadolinium enhancement) + FDG-PET — cornerstone of cardiac sarcoidosis detection; ECG/Holter for conduction disease/arrhythmia. - MRI brain/spine + CSF (↑protein, lymphocytic pleocytosis, ↑CSF ACE) for neurosarcoidosis. - Ophthalmologic slit-lamp exam (uveitis screening — recommended in all patients).

Differential diagnosis: tuberculosis & other mycobacterial/fungal infection, chronic beryllium disease (clinically identical — BeLPT distinguishes), lymphoma, hypersensitivity pneumonitis, granulomatosis with polyangiitis, IgG4-related disease, common variable immunodeficiency–associated granulomatous disease, Blau syndrome/NOD2 (pediatric), sarcoid-like reactions to malignancy or checkpoint-inhibitor immunotherapy.

Genetic testing: not used for diagnosis (polygenic); research/HLA-typing only (DRB103 for prognosis). No screening program*; cascade/newborn screening N/A.

11. Outcome / Prognosis

Overall mortality: low overall — death in roughly 5–10% of patients; mortality is rising in some registries. Leading causes: progressive pulmonary fibrosis with respiratory failure / pulmonary hypertension (esp. US/Europe) and cardiac sarcoidosis (sudden death, arrhythmia, heart failure) (esp. Japan).
Prognosis by phenotype: Löfgren syndrome → excellent (>85–90% remission); lupus pernio, cardiac, neuro, Stage IV fibrotic, and multiorgan disease in Black patients → worse.
Morbidity/QoL: fatigue, dyspnea, depression, and small-fiber neuropathy dominate disability; steroid toxicity is a major iatrogenic morbidity (drives the steroid-sparing agenda below).
Complications: pulmonary fibrosis, pulmonary hypertension (SAPH), aspergilloma/mycetoma in fibrocavitary disease, complete heart block / ventricular arrhythmia / sudden cardiac death, blindness (untreated uveitis), nephrocalcinosis/renal failure (hypercalcemia), neuroendocrine dysfunction.
Prognostic factors: Scadding stage, lupus pernio, cardiac/neuro involvement, race, age >40 at onset, splenomegaly, need for treatment >6 months, and biomarkers (persistently ↑sIL-2R, FDG-PET activity). HLA-DRB1*03:01 = favorable.

12. Treatment

Guidelines: ERS 2021 treatment guideline (Baughman, Wells et al., Eur Respir J 2021;58(6):2004079; PMID 34140301 ✓) and BTS 2021. Many patients (esp. asymptomatic Stage I/Löfgren) need no treatment; treat to preserve organ function/QoL.

Stepwise pharmacotherapy (suggest MAXO terms; treatment_term NCIT:C15986 Pharmacotherapy + CHEBI therapeutic_agent): 1. First-line: oral glucocorticoids (prednisone) — for symptomatic/threatened-organ disease; ERS advises limiting to a 3–6 month trial, maintenance <10 mg/day. MAXO: MAXO:0000950 supportive? better generic Pharmacotherapy; CHEBI:8378 prednisone / CHEBI:8382 prednisolone. 2. Second-line steroid-sparing: methotrexate (CHEBI:44185; most-used), azathioprine (CHEBI:2948), leflunomide, mycophenolate, hydroxychloroquine (CHEBI:5801; cutaneous/hypercalcemia/neuro). 3. Third-line biologics: anti-TNF-α — infliximab (NCIT:C1296; therapeutic_modality MONOCLONAL_ANTIBODY) for refractory pulmonary, neuro, lupus pernio; adalimumab alternative. ERS: conditional recommendation, low-quality evidence. Real-world data: Respir Res 2022.

Emerging / mechanism-targeted: - JAK inhibitors — tofacitinib (CHEBI:71200): striking responses in cutaneous and multiorgan sarcoidosis; reverses the IFN-γ/JAK-STAT granuloma transcriptome (Damsky et al., NEJM 2018;379:2540–2546; PMID 30586519 ✓ / DOI 10.1056/NEJMoa1805958); also ruxolitinib, laryngeal case PMID 39295484 ⚠. - Efzofitimod (ATYR1923) — first-in-class neuropilin-2 (NRP2) immunomodulator. Phase 3 EFZO-FIT (Sept 2025): MISSED primary endpoint (steroid-dose reduction 2.79 vs 3.52 mg, p=0.33) but 52.6% vs 40.2% achieved complete steroid withdrawal with QoL/FVC benefit and good safety (aTyr topline release; NCT03824392 / EFZO-FIT NCT05415137 ⚠). - mTOR-pathway and CCL24/CCR3 inhibition are preclinical targets (see §6).

Organ-specific/interventional: - Cardiac: immunosuppression + ICD (device; arrhythmia/sudden-death prevention), pacemaker for heart block, antiarrhythmics. - Hypercalcemia: corticosteroids, hydroxychloroquine, low calcium/vit-D intake, sun avoidance. - End-stage: lung transplantation (MAXO:0010039 organ transplantation) / heart transplant; pulmonary rehabilitation; treat SAPH. - Supportive: fatigue/neuropathy management, antidepressants, pulmonary rehab (MAXO:0000950 supportive care; MAXO:0000011 physical therapy).

Pharmacogenomics: TPMT/NUDT15 genotyping before azathioprine (myelotoxicity risk; CPIC guideline). Steroid response heterogeneous.

13. Prevention

No primary prevention exists (cause unknown, not vaccine-preventable). Risk reduction limited to avoiding implicated occupational/inhalational exposures (e.g., WTC-type dust, beryllium control) — more occupational hygiene than personal prevention.
Secondary prevention: early ophthalmologic screening (prevent uveitis blindness), baseline + periodic ECG/cardiac screening (detect occult cardiac sarcoidosis → prevent sudden death), monitoring calcium/renal function.
Tertiary prevention: steroid-sparing strategies to prevent iatrogenic harm; FDG-PET/CMR-guided escalation to prevent fibrosis; ICD in high-risk cardiac disease.
Counseling: family risk is modestly elevated but routine genetic counseling/testing is not indicated (polygenic). Smoking cessation advised for general health despite the inverse risk association.
No immunization, no prophylactic medication, no public-health/vector measures (non-infectious).

14. Other Species / Natural Disease

Taxonomy: primarily a human (NCBITaxon:9606) disease — no validated naturally occurring animal homolog.
Veterinary: A clinically and histologically analogous idiopathic systemic granulomatous disease occurs in horses (NCBITaxon:9796) — equine sarcoidosis / equine systemic granulomatous disease (generalized granulomatous dermatitis ± internal organs). Granulomatous diseases occur in dogs/cats but are not true sarcoidosis homologs.
Comparative biology: the closest experimental analog is chronic beryllium disease (HLA-DPB1*Glu69-restricted) — a defined-antigen model of an otherwise sarcoidosis-like granulomatosis.
Zoonosis: none — sarcoidosis is non-infectious and non-transmissible.

15. Model Organisms

No model fully recapitulates human sarcoidosis; granuloma-focused models dominate (review, Front Immunol 2020).

Mouse (NCBITaxon:10090):
mTORC1/Tsc2-knockout macrophage model (Linke 2017, PMID 28092373 ✓): myeloid Tsc2 deletion → constitutive mTORC1 → spontaneous progressive granulomas; best genetic model, recapitulates macrophage proliferation/granuloma growth and progression marker biology. Conditional/Cre-lox (LysM-Cre).
mTORC1-dependent cardiac sarcoidosis mouse (2023, PMID 37750561 ✓): models cardiac granulomas/conduction disease.
Antigen-induced granuloma models: C. acnes, mycobacterial mKatG/ESAT-6, and bead/multiwall carbon nanotube + sarcoid-antigen induction models reproduce granuloma histology.
Adoptive-transfer / Th17 / IL-33 Treg-dysfunction models for immune mechanism.
In vitro / human: granuloma-in-a-dish — PBMC-derived granuloma models (with C. acnes or beads); iPSC-derived macrophages; BAL-cell transcriptomics (GEO datasets).
Limitations: no single model captures the multiorgan, chronic-relapsing, antigen-ambiguous human disease; most are acute/induced or single-pathway (mTORC1) and lack the human HLA-restricted adaptive arm.
Resources: MGI (Tsc2 conditional alleles), IMPC/KOMP, GEO/ArrayExpress for transcriptomic datasets.

Suggested dismech modeling anchors

Module reuse: link fibrotic pulmonary endpoint to fibrotic_response (tissue injury → inflammation → mesenchymal activation → ECM → organ dysfunction); cardiac arrhythmic complications could cross-reference electrical-remodeling concepts. Consider whether a new granuloma-formation mechanism module (Th1/Th17 → macrophage epithelioid differentiation → mTORC1-driven granuloma) is warranted given recurrence across granulomatous diseases (TB, Crohn, berylliosis, Blau).
Inheritance: model as multifactorial/polygenic, GENO susceptibility associations (HLA-DRB1, BTNL2, ANXA11) — not Mendelian causal variants.
Evidence sourcing: core mechanism = MODEL_ORGANISM (Linke mouse) + IN_VITRO; epidemiology/prognosis/treatment = HUMAN_CLINICAL; mTORC1 marker work mixes IN_VITRO + HUMAN_CLINICAL — split evidence items accordingly.

Key References (verify all before committing)

#	Citation	ID
1	Grunewald J, et al. Sarcoidosis. Nat Rev Dis Primers 2019;5:45.	DOI 10.1038/s41572-019-0096-x; PMID 31273209 ⚠
2	Crouser ED, et al. Diagnosis and Detection of Sarcoidosis: ATS Clinical Practice Guideline. Am J Respir Crit Care Med 2020;201(8):e26–e51.	PMID 32293205 ✓
3	Baughman RP, Wells AU, et al. ERS guidelines on treatment of sarcoidosis. Eur Respir J 2021;58(6):2004079.	PMID 34140301 ⚠
4	Linke M, et al. Chronic mTORC1 signaling induces macrophage granuloma formation and marks sarcoidosis progression. Nat Immunol 2017;18:293–302.	PMID 28092373 ✓; DOI 10.1038/ni.3655
5	Damsky W, et al. Tofacitinib Treatment and Molecular Analysis of Cutaneous Sarcoidosis. NEJM 2018;379:2540–2546.	PMID 30586519 ✓
6	Rossides M, et al. Sarcoidosis: Epidemiology and clinical insights. J Intern Med 2023.	DOI 10.1111/joim.13629 ⚠
7	Morais A, et al. ANXA11/BTNL2/HLA and sarcoidosis course. Clin Respir J 2018.	PMID 27662826 ✓
8	eQTL polymorphisms & progressive complicated sarcoidosis. 2024.	PMID 38390497 ✓
9	mTORC1-dependent mouse model for cardiac sarcoidosis. JAHA 2023.	PMID 37750561 ✓
10	Sarcoidosis: molecular mechanisms and therapeutic strategies. 2025.	PMC11794924
11	aTyr Pharma, EFZO-FIT Phase 3 topline (efzofitimod), Sept 2025.	press release

Sources (web): - Grunewald 2019 Nat Rev Dis Primers - ATS 2020 diagnosis guideline (Crouser) - ERS 2021 treatment guideline - Linke 2017 mTORC1, Nat Immunol - Damsky 2018 tofacitinib, NEJM - Rossides 2023 epidemiology, J Intern Med - Sarcoidosis Epidemiology: Race Matters - Morais 2018 ANXA11/BTNL2/HLA, PMID 27662826 - eQTL progressive sarcoidosis, PMID 38390497 - Cardiac sarcoidosis mTORC1 mouse, PMID 37750561 - Molecular mechanisms & therapeutics 2025, PMC11794924 - Immunopathogenesis review, J Autoimmun 2024 - mTORC1/JAK-STAT/NLRP3 in patients, PMC10454122 - sIL-2R diagnostic accuracy, PMC6797090 - aTyr EFZO-FIT Phase 3 topline - ANXA11 association, Genes & Immunity - Sarcoidosis models review, Front Immunol 2020 - Latent microbial reactivation review 2025, PMC12362391 - England population-based study 2024, PMC12002749

Bottom line: sarcoidosis is best modeled in dismech as a complex (polygenic + environmental) immune granulomatous disease whose pathophysiology runs HLA-restricted antigen presentation → Th1/Th17.1 activation → IFN-γ/TNF-driven macrophage epithelioid differentiation → mTORC1-sustained non-caseating granuloma → resolution (Treg) or TGF-β/M2 fibrosis. The two highest-value, well-verified mechanistic citations are Linke 2017 (mTORC1, PMID 28092373) and Crouser 2020 (ATS diagnosis, PMID 32293205); the freshest clinical development is the 2025 efzofitimod Phase 3 miss-but-signal. Re-verify every PMID with just fetch-reference before it lands in a YAML evidence block.

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1. Disease Information

Edison Scientific Literature 62 citations 2026-04-26T20:13:58.309383

1. Disease Information

1.1 Definition and overview

Sarcoidosis is described as a complex multisystem immune-mediated disorder in which inflammatory cells accumulate and organize into non-caseous granulomas within affected organs (kim2024advancesincellular pages 1-5). A recent immunopathogenesis review defines it as “a granulomatous disease of unknown cause, triggered by an unidentified antigen,” with the histopathologic hallmark being “discrete, well-formed, non-necrotizing granulomas composed of epithelioid histiocytes and multinucleated giant cells surrounded by lymphocytes, plasma cells, and fibroblasts” (vagts2025immunopathogenesisofsarcoidosis pages 1-2).

1.2 Key identifiers (with availability in retrieved sources)

MONDO: MONDO:0019338 (Open Targets disease object) (he2025globalburdenof pages 1-2).
ICD-10: D86–D86.2, D86.9 (used in GBD-based epidemiologic analysis for case definition) (he2025globalburdenof pages 1-2).
MeSH / ICD-11 / Orphanet / OMIM (disease entry): Not directly retrievable from the current evidence set; additional database-specific queries (MeSH Browser, ICD-11, Orphanet, OMIM) would be required for authoritative IDs.

1.3 Synonyms / alternative names

The retrieved sources primarily use “sarcoidosis” and organ qualifiers (pulmonary sarcoidosis, extrapulmonary sarcoidosis, muscular sarcoidosis). Formal synonym lists were not present in the extracted texts; common clinical variants highlighted include Löfgren syndrome (acute presentation) (weeratunga2024immunemechanismsof pages 1-2, vagts2025immunopathogenesisofsarcoidosis pages 1-2).

1.4 Evidence provenance

This report synthesizes aggregated disease-level resources (reviews, meta-analyses, registry cohorts, and clinical trial registries), not individual EHR case notes, except where cohorts explicitly derive from health-system databases (e.g., Clalit) (patt2024elevatedmortalityrisk pages 1-2, patt2024elevatedmortalityrisk pages 2-3).

2. Etiology

2.1 Causal factors (current consensus)

Sarcoidosis etiology remains unknown; leading models invoke a triggering antigen in a genetically predisposed host leading to persistent immune activation and granuloma formation (vagts2025immunopathogenesisofsarcoidosis pages 1-2, papanikolaou2025phenotypesandendotypes pages 4-6).

2.2 Genetic risk factors (susceptibility/severity loci)

A 2023 integrated GWAS–eQTL approach (European and African ancestry cohorts) reported that dysregulated innate immunity and MHC-related pathways are implicated in sarcoidosis risk/severity and validated loci including NOTCH4, IL27RA, BTNL2, ANXA11, and HLA-DRB1 (doi:10.31488/ejrm.137) (casanova2023examinationofeqtl pages 1-3). This supports a polygenic architecture with strong immunogenetic involvement.

Ontology (gene) suggestions: HGNC symbols: BTNL2, ANXA11, HLA-DRB1, NOTCH4, IL27RA (casanova2023examinationofeqtl pages 1-3).
Mechanism linkage: antigen presentation / MHC class II and innate immune response pathways (casanova2023examinationofeqtl pages 1-3, papanikolaou2025phenotypesandendotypes pages 4-6).

2.3 Environmental and infectious risk factors

The retrieved mechanistic phenotype/endotype review notes infectious agents such as Mycobacterium species and Propionibacterium acnes as implicated candidates and describes innate immune sensing via TLR pathways in antigen presentation contexts (papanikolaou2025phenotypesandendotypes pages 4-6). (This reflects hypothesized triggers; causal proof is not established.)

2.4 Protective factors

A protective-factor evidence base was not directly extractable from the retrieved documents.

2.5 Gene–environment interactions

Direct GxE effect sizes were not provided in the retrieved evidence set.

3. Phenotypes (clinical manifestations)

3.1 Core clinical phenotype domain

Sarcoidosis has heterogeneous organ involvement. The lungs dominate clinical burden, with pulmonary/intrathoracic involvement reported up to ~90–95% across sources (kim2024advancesincellular pages 1-5, vagts2025immunopathogenesisofsarcoidosis pages 1-2, baratella2025ctimagingfeatures pages 1-3). Extrapulmonary involvement is common, with review-level estimates of ~30–50% (starshinova2024chronicsarcoidosisdiagnostic pages 2-3).

3.2 Example organ involvement frequencies (from retrieved sources)

From a 2024 chronic sarcoidosis review: extrapulmonary disease ~30–50%, with reported organ frequencies including cutaneous 15.9%, ocular 11.8%, and neurologic 4.6% (starshinova2024chronicsarcoidosisdiagnostic pages 2-3). Ocular complications include posterior uveitis (5–28% of ocular cases), panuveitis (up to 48%), retinal vasculitis (18%), and retinal neovascularization (1–5%) (starshinova2024chronicsarcoidosisdiagnostic pages 14-15).

3.3 Onset and course (high-level)

Löfgren syndrome is emphasized as an acute presentation that often resolves: about 80% resolution within 2 years in one review (weeratunga2024immunemechanismsof pages 1-2). Chronic/progressive disease is described in “approximately 10 to 40%” in an immunopathogenesis review excerpt (vagts2025immunopathogenesisofsarcoidosis pages 1-2).

3.4 Quality of life

Quality-of-life measures are explicitly emphasized in modern care frameworks (e.g., fatigue and health status instruments appear as key outcomes in treatment considerations) (dhanani2025immunosuppressivetherapiesin pages 3-4, dhanani2025immunosuppressivetherapiesin pages 10-12). Disease-associated fatigue is a major patient-reported concern; however, standardized QoL effect sizes were not extractable from the retrieved passages.

3.5 HPO term suggestions (non-exhaustive; mapped to retrieved phenotype domains)

Pulmonary involvement: HP:0002094 (Dyspnea), HP:0002104 (Pulmonary fibrosis), HP:0006510 (Restrictive ventilatory defect).
Lymphadenopathy: HP:0002716 (Lymphadenopathy).
Skin: HP:0000988 (Skin rash); granulomatous dermatitis-related terms.
Eye: HP:0000554 (Uveitis), HP:0000602 (Retinal vasculitis).
Hypercalcemia: HP:0003072 (Hypercalcemia).

(These are ontology suggestions; frequency and exact mapping should be validated against HPO definitions and organ-specific sarcoidosis cohorts.)

4. Genetic/Molecular Information

4.1 “Causal genes” vs susceptibility genes

Sarcoidosis is generally treated as complex/polygenic rather than a classic monogenic disorder. The retrieved evidence supports susceptibility and severity loci (e.g., HLA region, BTNL2, ANXA11, NOTCH4, IL27RA) rather than single-gene causality (casanova2023examinationofeqtl pages 1-3).

4.2 Pathogenic variants (status in retrieved evidence)

Specific variant nomenclature (HGVS) and ClinVar classifications were not present in extracted content; therefore, variant-level curation (pathogenic/likely pathogenic/VUS) cannot be completed from this evidence set.

4.3 Modifier genes / severity genetics

The integrated eQTL/GWAS severity analysis suggests multiple loci and pathways associated with complicated/progressive disease, emphasizing innate immunity and MHC class II involvement (casanova2023examinationofeqtl pages 1-3).

4.4 Epigenetic information

No direct methylation/histone modification datasets were extractable from the retrieved excerpts.

5. Environmental Information

The retrieved sources emphasize possible environmental/occupational and infectious triggers at a conceptual level, but do not provide a curated list of exposures with quantitative risk estimates in the available passages (papanikolaou2025phenotypesandendotypes pages 4-6).

6. Mechanism / Pathophysiology

6.1 Causal chain (trigger → granuloma → organ dysfunction)

A coherent mechanistic chain described across sources is: 1) Triggering antigen/exposure in a susceptible host →
2) Antigen presentation by macrophages/dendritic cells via MHC-II and innate sensing (e.g., TLR-related pathways) →
3) CD4+ T-cell polarization and cytokine production (classically IFN-γ; Th1/Th17/Th17.1) →
4) Macrophage differentiation into epithelioid cells and multinucleated giant cells, organizing granulomas →
5) Either resolution or persistence with tissue remodeling/fibrosis and organ impairment (lung restriction, DLCO decline), with potential extrapulmonary damage (vagts2025immunopathogenesisofsarcoidosis pages 1-2, papanikolaou2025phenotypesandendotypes pages 4-6).

6.2 Key immune pathways and cell types (with ontology suggestions)

Dominant immune phenotype: IFN-γ/Th1 with Th17/Th17.1 contributions (vagts2025immunopathogenesisofsarcoidosis pages 1-2, papanikolaou2025phenotypesandendotypes pages 4-6).

Granuloma cellular composition: macrophages/epithelioid cells/giant cells with surrounding lymphocytes; monocytes/neutrophils/fibroblasts can contribute (weeratunga2024immunemechanismsof pages 1-2, kim2024advancesincellular pages 1-5).

Ontology suggestions: * GO (biological processes): antigen processing and presentation (MHC class II), T cell activation, cytokine-mediated signaling pathway, granuloma formation, extracellular matrix organization, fibrosis. * CL (cell types): CL:0000540 (macrophage), CL:0000624 (CD4-positive, alpha-beta T cell), fibroblast, dendritic cell.

6.3 Recent developments (2023–2024 priority): single-cell / spatial / metabolic mechanisms

(a) Macrophage metabolic reprogramming and PPP (JCI 2023): A 2023 JCI study using single-cell RNA-seq in sarcoidosis reported an increase of TREM2-positive macrophages expressing ACE and lysozyme in cutaneous sarcoidosis granulomas and found macrophages to be “hypermetabolic,” particularly with activation of the pentose phosphate pathway (PPP); PPP enzyme expression (e.g., FBP1) was elevated in lesions and serum, and PPP inhibitors attenuated granuloma formation in in vitro and murine models—supporting PPP as a potential therapeutic target (doi:10.1172/jci171088) (dhanani2025immunosuppressivetherapiesin pages 10-12).

(b) Spatial transcriptomics in muscular sarcoidosis (Cells 2023): Spatial transcriptomics of two muscular sarcoidosis patients identified transcriptomic clusters spanning granuloma/perigranuloma and surrounding muscle. Granuloma regions showed immune activation (T-lymphocyte and monocyte/macrophage cytokines), while perigranuloma showed extracellular matrix and TGF-β signaling signatures. Proximity to granuloma correlated with stronger interferon/TNF/IL-1/IL-4/IL-6 response signatures and fibrotic replacement signals (doi:10.3390/cells12232747) (starshinova2024chronicsarcoidosisdiagnostic pages 26-27).

(c) High-resolution granuloma interrogation (JCI Review 2024): A 2024 JCI review highlights that “recent high-resolution studies of the granuloma in situ” using single-cell and spatial methods are clarifying plausible mechanisms in sarcoidosis and enabling comparative analysis with tuberculosis granulomas (doi:10.1172/jci175264) (weeratunga2024immunemechanismsof pages 1-2).

6.4 Imaging/biopsy advances linked to mechanism

A 2024 review of imaging and tissue-based methods emphasizes advanced approaches such as spatial transcriptomics and MALDI mass spectrometry imaging to map granuloma biochemistry and spatial organization (doi:10.1152/ajpcell.00507.2023) (kim2024advancesincellular pages 1-5).

7. Anatomical Structures Affected

7.1 Organ-level involvement

Most commonly affected: lungs and intrathoracic lymph nodes (up to ~90–95%) (kim2024advancesincellular pages 1-5, baratella2025ctimagingfeatures pages 1-3). Common extrapulmonary targets include skin, eyes, and heart, with neurologic and renal involvement less frequent but clinically high impact (kim2024advancesincellular pages 1-5, starshinova2024chronicsarcoidosisdiagnostic pages 2-3).

7.2 UBERON suggestions (non-exhaustive)

Lung (UBERON:0002048)
Mediastinal/hilar lymph nodes (regional lymph node structures)
Skin (UBERON:0002097)
Eye (UBERON:0000970)
Heart (UBERON:0000948)
Skeletal muscle (UBERON:0001134) (muscular sarcoidosis study) (starshinova2024chronicsarcoidosisdiagnostic pages 26-27)

8. Temporal Development

Typical onset: peaks reported in young adults (20–39 years) in one epidemiology overview (kim2024advancesincellular pages 1-5).
Course patterns: acute (e.g., Löfgren syndrome) with high spontaneous resolution vs chronic/progressive disease (weeratunga2024immunemechanismsof pages 1-2, vagts2025immunopathogenesisofsarcoidosis pages 1-2).
Fibrosis progression: a minority develop fibrotic lung disease; CT fibrosis extent is linked to prognosis and thresholds of functional decline are used clinically (baratella2025ctimagingfeatures pages 3-4).

9. Inheritance and Population

9.1 Epidemiology (incidence, prevalence, demographics)

Population ranges and geographic variation: * Reported prevalence ~4.7–64 per 100,000 and incidence ~1–35.5 per 100,000/year in a recent registry paper’s contextual epidemiology discussion (guttmannducke2025firstinsightsand pages 1-2).
Marked geographic differences: Scandinavia/UK ~64 per 100,000 and African American populations ~39 per 100,000, compared with South Korea 4.67 and Japan 3.7 per 100,000* (kim2024advancesincellular pages 1-5).

Example real-world registry demographics: * Vienna registry (2022–2023; n=199): mean age 52±13, women 57.5%; chest X-ray stage distribution 1:34.5%, 2:46%, 3:9.5%, 4:6% (guttmannducke2025firstinsightsand pages 1-2).

9.2 Genetic architecture / inheritance

Evidence supports polygenic susceptibility (HLA and non-HLA loci), rather than Mendelian inheritance, consistent with multifactorial disease (casanova2023examinationofeqtl pages 1-3).

10. Diagnostics

10.1 Diagnostic criteria (core consensus)

A 2024 review explicitly states diagnosis is based on three main criteria: (1) clinical presentation, (2) histologic detection of non-caseating granulomas in ≥1 tissue sample, and (3) exclusion of alternative granulomatous diseases (starshinova2024chronicsarcoidosisdiagnostic pages 2-3). A 2025 PET/CT meta-analysis similarly describes accepted diagnosis requiring compatible clinical picture, radiologic evidence, and histologic demonstration of non-necrotising granulomatous disease (donnelly2025metaanalysisof[18f]fdgpetct pages 1-2).

10.2 Histopathology

Granulomas are composed largely of macrophage-derived epithelioid and giant cells with surrounding lymphocytes (kim2024advancesincellular pages 1-5, starshinova2024chronicsarcoidosisdiagnostic pages 14-15).

10.3 Laboratory tests / biomarkers

Supportive biomarkers include: * Serum ACE (produced by monocytes/macrophages/epithelioid cells) reported to correlate with granuloma burden and radiologic stages II–III and may reflect activity/extrathoracic involvement (starshinova2024chronicsarcoidosisdiagnostic pages 15-17, starshinova2024chronicsarcoidosisdiagnostic pages 14-15).
Soluble IL-2 receptor (sIL-2R) as a marker of Th1 activation; may predict progression/relapse (starshinova2024chronicsarcoidosisdiagnostic pages 15-17).
Hypercalcemia with low PTH and normal/low 25-hydroxyvitamin D can occur (starshinova2024chronicsarcoidosisdiagnostic pages 15-17, starshinova2024chronicsarcoidosisdiagnostic pages 14-15).

BAL findings may show lymphocytosis (>15%) and CD4/CD8 ≥3.5 but are not specific (starshinova2024chronicsarcoidosisdiagnostic pages 15-17).

10.4 Imaging

HRCT: preferred over CXR for sensitivity and evaluation of complications (baratella2025ctimagingfeatures pages 3-4, baratella2025ctimagingfeatures pages 1-3).
FDG-PET/CT: a 2025 meta-analysis (search through Sep 2023) reported pooled sensitivity 0.971 and specificity 0.873 for suspected pulmonary sarcoidosis; SUVmax reduction correlated with improved FVC and DLCO and may help guide immunosuppression decisions (doi:10.1007/s00330-024-10949-4) (donnelly2025metaanalysisof[18f]fdgpetct pages 1-2).

10.5 Differential diagnosis

Imaging reviews stress differentiation from tuberculosis, silicosis, malignancy, organizing pneumonia, hypersensitivity pneumonitis, etc., and emphasize integrating clinical/radiologic/pathologic evidence with exclusion of alternatives (baratella2025ctimagingfeatures pages 1-3).

11. Outcome / Prognosis

11.1 Mortality and survival (recent real-world estimates)

A 2024 population-based cohort study (Clalit Health Services; incident cases 2000–2016) reported higher mortality in sarcoidosis than controls (17.7% vs 10.6%), with adjusted all-cause mortality HR 1.79 (95% CI 1.64–1.96) and the highest hazard in the first year post-diagnosis (patt2024elevatedmortalityrisk pages 1-2). Another excerpt reports first-year multivariable HR 2.99 (95% CI 2.39–3.75), and persistent but lower hazards thereafter (patt2024elevatedmortalityrisk pages 8-9). Predictors included age at diagnosis, male sex, and comorbidity burden (patt2024elevatedmortalityrisk pages 1-2, patt2024elevatedmortalityrisk pages 8-9).

11.2 Prognostic functional markers

Imaging-focused reviews highlight functional thresholds associated with progression/response such as ≥5% decline in FVC and ≥10% decline in DLCO, and note that fibrosis extent (e.g., >20% parenchymal fibrosis on CT) correlates with worse outcomes (baratella2025ctimagingfeatures pages 3-4).

12. Treatment

12.1 Current standard pharmacotherapy (guideline-aligned approach)

A practical evidence-based review states oral glucocorticoids remain first-line for symptomatic pulmonary sarcoidosis (typical starting prednisone 20–40 mg/day) with tapering over 6–18 months guided by response; steroid-sparing agents are often required due to toxicity (doi:10.3390/jcm14196828) (dhanani2025immunosuppressivetherapiesin pages 1-3). Second-line agents include methotrexate (preferred), azathioprine, leflunomide, and mycophenolate; refractory disease options include anti-TNF agents (infliximab, adalimumab) and emerging approaches such as JAK inhibitors, rituximab, and repository corticotropin injection (RCI) (dhanani2025immunosuppressivetherapiesin pages 3-4, dhanani2025immunosuppressivetherapiesin pages 10-12).

MAXO suggestions (non-exhaustive): glucocorticoid therapy; methotrexate therapy; TNF inhibitor therapy; antifibrotic therapy; immunosuppressive therapy; JAK inhibitor therapy.

12.2 Recent developments (high-priority evidence)

Methotrexate as first-line alternative (NEJM 2025): In the PREDMETH noninferiority trial (NCT04314193), methotrexate was noninferior to prednisone for 24-week improvement in % predicted FVC (+6.11 vs +6.75 points); adverse event profiles differed (doi:10.1056/NEJMoa2501443) (kahlmann2025firstlinetreatmentof pages 1-2). This is a major development supporting steroid-minimizing strategies.

12.3 Biologics and advanced immunomodulators

Infliximab (anti-TNF): ClinicalTrials.gov record NCT00073437 describes a multicenter Phase 3 randomized, double-blind, placebo-controlled trial (n=139) assessing infliximab (3 or 5 mg/kg) with primary endpoint change in % predicted FVC at week 24, and cites associated publications including PMID 16840744 and PMID 18256069 (NCT00073437 chunk 1).
Adalimumab: NCT00311246 (progressive sarcoidosis; n=11) used adalimumab 40 mg SC weekly; primary endpoint was change in FVC from screening to week 24 (NCT00311246 chunk 2).

12.4 Antifibrotics / progressive fibrotic sarcoidosis trials

Pirfenidone: NCT03260556 is a Phase 4 randomized, triple-masked placebo-controlled trial (estimated n=60) in progressive fibrotic sarcoidosis; primary endpoint “time until clinical worsening” over two years (NCT03260556 chunk 1).
Nintedanib: NCT06479603 is recruiting and compares nintedanib vs standard of care in fibrotic sarcoidosis; the provided chunk includes fibrosis-based inclusion criteria but does not show endpoints/phase/enrollment in that excerpt (NCT06479603 chunk 2).

12.5 Efzofitimod (ATYR1923) — steroid-sparing investigational therapy

NCT03824392 is a completed early study of IV ATYR1923/efzofitimod; registry chunk cites related publications including PMID 37854715 and PMID 36356657 (NCT03824392 chunk 2). (Detailed endpoints/phase are not present in the extracted chunk.)

13. Prevention

No disease-specific primary prevention strategies were identified in the retrieved sources. Prevention in practice centers on (i) avoiding unnecessary immunosuppression in self-limited disease, (ii) monitoring and mitigating treatment complications, and (iii) addressing exposure hypotheses where relevant, but quantitative prevention evidence was not extractable from the provided texts.

14. Other Species / Natural Disease

No naturally occurring veterinary sarcoidosis analogs were identified in the retrieved evidence set.

15. Model Organisms

The PPP/macrophage study reports both in vitro giant cell and in vivo murine granuloma models in which PPP inhibitors attenuated granuloma formation, supporting tractable experimental models for granulomatous inflammation and therapeutic targeting (dhanani2025immunosuppressivetherapiesin pages 10-12). Additional organism-specific model catalogs (MGI/IMPC) were not retrieved in this run.

Expert opinions and authoritative analysis (from high-authority sources)

The JCI 2024 review frames sarcoidosis as a “complex immune-mediated disease characterized by clusters of immune cells called granulomas” and emphasizes insights emerging from high-resolution single-cell/spatial studies (doi:10.1172/jci175264) (weeratunga2024immunemechanismsof pages 1-2).
The immunopathogenesis review emphasizes an IFN-γ/Th1–Th17 axis and dysregulated innate–adaptive crosstalk as central drivers of granuloma persistence and fibrotic progression (doi:10.1055/a-2716-5737) (vagts2025immunopathogenesisofsarcoidosis pages 1-2).
The NEJM 2025 PREDMETH trial provides the strongest recent clinical evidence supporting methotrexate as an initial therapy option with comparable short-term lung function improvement to prednisone (doi:10.1056/NEJMoa2501443) (kahlmann2025firstlinetreatmentof pages 1-2).

Key gaps and limitations of this evidence set

Several requested identifier systems (MeSH, ICD-11, Orphanet, OMIM disease entry) were not present in the retrieved texts and cannot be reliably asserted without dedicated database queries.
Variant-level (ClinVar/ACMG) pathogenic variant curation is not possible from the extracted passages.
Some trial details for efzofitimod Phase 3 (NCT05415137), tofacitinib trials, and the nintedanib record endpoints were not contained in the retrieved chunks; additional ClinicalTrials.gov sections would be required for full endpoint extraction.

References

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Sarcoidosis (MONDO:0019338): A Comprehensive Disease Characteristics Report

openscientist-autonomous 39 citations 2026-07-26T02:53:30.429628

Sarcoidosis (MONDO:0019338): A Comprehensive Disease Characteristics Report

Disease: Sarcoidosis · MONDO: MONDO:0019338 · Category: Immune Report date: 2026-07-26 · Evidence sources: human clinical studies, GWAS, model organisms (mouse), in vitro/omics. PMIDs cited inline.

Summary

Sarcoidosis is a multisystem, immune-mediated inflammatory disease of unknown cause, defined pathologically by noncaseating epithelioid-cell granulomas that most commonly involve the lungs and intrathoracic lymph nodes but can affect virtually any organ (skin, eyes, heart, nervous system, liver, spleen, and kidneys). The prevailing model is that sarcoidosis arises when a genetically susceptible host (strongest signals in the HLA class II region plus BTNL2, ANXA11, and NOTCH4) mounts an exaggerated, HLA-restricted CD4+ Th1/Th17 granulomatous response to persistent, poorly degradable antigens. The leading candidate antigens are remnant microbial proteins—particularly Mycobacterium tuberculosis catalase-peroxidase (mKatG), ESAT-6, and superoxide dismutase A (SodA)—and environmental/occupational bioaerosols, with a paradoxical inverse association with cigarette smoking.

The disease course is strikingly bimodal: roughly 70% of patients experience near-complete spontaneous or treatment-induced remission within two years (best exemplified by the acute HLA-DRB103–linked Löfgren syndrome), while approximately 30% (enriched for HLA-DRB115) develop chronic, progressive disease that can lead to pulmonary fibrosis, cardiac and neurological involvement, and rising, racially disparate mortality. A rare monogenic pediatric form—Blau syndrome / early-onset sarcoidosis—is caused by autosomal-dominant gain-of-function mutations in NOD2 (CARD15) and presents with the triad of arthritis, dermatitis, and uveitis.

Mechanistically, aberrant mTORC1 activation in macrophages and fibroblasts has emerged as a causal driver of granuloma formation and a druggable target. Diagnosis remains one of exclusion, requiring compatible clinico-radiologic features plus granuloma histology; soluble IL-2 receptor (sIL-2R) outperforms serum ACE as a supporting biomarker. Treatment escalates from corticosteroids to steroid-sparing agents (methotrexate, azathioprine) and anti-TNF therapy (infliximab), with emerging targeted options including the first-in-class neuropilin-2 immunomodulator efzofitimod, mTOR inhibitors (sirolimus), and JAK inhibitors.

1. Disease Information

Overview. Sarcoidosis is a chronic, systemic granulomatous disorder of unknown etiology characterized by the formation of noncaseating (non-necrotizing) epithelioid granulomas. It predominantly involves the lungs and thoracic lymph nodes (>90% of cases) but is a true multisystem disease. As the recent review notes, diagnosis relies on "compatible clinico-radiologic features plus biopsy showing noncaseating epithelioid granulomas and exclusion of infection/malignancy" (PMID: 41651390).

Key identifiers.

Resource	Identifier
MONDO	MONDO:0019338
ICD-10	D86 (D86.0 pulmonary, D86.2 lung with lymph nodes, D86.3 skin, D86.8 other/neurosarcoidosis, D86.9 unspecified)
ICD-11	4B20
MeSH	D012507 (Sarcoidosis)
Orphanet	ORPHA:797
OMIM	181000 (Sarcoidosis, susceptibility, SS1); 186580/609464 (Blau syndrome / early-onset sarcoidosis, NOD2)

Synonyms / alternative names. Besnier-Boeck-Schaumann disease; Boeck's sarcoid; Löfgren syndrome (acute form); Blau syndrome / early-onset sarcoidosis (monogenic pediatric form). Organ-specific terms: cardiac sarcoidosis, neurosarcoidosis, ocular/sarcoid uveitis, cutaneous sarcoidosis (e.g., lupus pernio).

Information source. Information is derived from a mixture of aggregated disease-level resources (OMIM, Orphanet, MeSH) and large individual-patient / EHR-based cohorts — e.g., the Swedish national register (n=9,665; PMID: 42498935), the US TriNetX network (>108 million patients; PMID: 41512253), and the VHA veteran cohort (n=23,745; PMID: 39521376).

2. Etiology

Disease causal factors. Sarcoidosis is best modeled as a gene–environment disease: the ACCESS study's central hypothesis was that "sarcoidosis occurs in genetically susceptible individuals through alteration in immune response after exposure to an environmental, occupational, or infectious agent" (PMID: 17684288). No single cause has been identified.

Genetic risk factors. A genome-wide association study in African Americans (818 cases/1,088 controls, replicated) and European Americans confirmed associations at HLA-DRA, HLA-DRB5, HLA-DRB1, BTNL2, and ANXA11, and identified NOTCH4 as an independent genome-wide-significant locus (rs715299, P = 6.51×10⁻¹⁰) (PMID: 22952805). Verbatim: "We identified a novel sarcoidosis-associated locus, NOTCH4, that reached genome-wide significance in the combined AA samples (rs715299, P(AA-meta) = 6.51 × 10(-10))... We replicated previous European GWAS associations within HLA-DRA, HLA-DRB5, HLA-DRB1, BTNL2, and ANXA11 in both our AA and EA datasets." HLA-C and HLA-B associations were significant in European Americans but not African Americans. The monogenic form (Blau syndrome) is caused by NOD2/CARD15 mutations (Section 4).

Environmental / occupational risk factors. The ACCESS case-control study (706 newly diagnosed cases + matched controls) found positive associations with agricultural employment (OR 1.46, 95% CI 1.13–1.89), occupational insecticide exposure (OR 1.61, CI 1.13–2.28), and musty-odor/mold-mildew (microbial bioaerosol) work environments (OR 1.62, CI 1.24–2.11) (PMID: 15347561). The World Trade Center disaster demonstrated an occupational trigger: "sarcoid-like" granulomatous pulmonary disease occurred among responders at a 6-year incidence of 192/100,000, nearly double in Black vs White responders (PMID: 21298693). Additional risk factors: female sex, African ancestry, obesity, and family history.

Protective factors. The most robust protective factor is cigarette smoking, which is inversely associated with sarcoidosis (ACCESS: ever-smoking OR 0.65, CI 0.51–0.82) (PMID: 15347561). Verbatim: "we observed elevated ORs for work in areas with musty odors (OR 1.62, CI 1.24-2.11) and with occupational exposure to insecticides (OR 1.61, CI 1.13-2.28), and a decreased OR related to ever smoking cigarettes (OR 0.65, CI 0.51-0.82)." Genetic protective factors include HLA-DRB101:01, HLA-DQA103:01, and HLA-DQB103:02 in a Czech cohort (PMID: 37153085), and the HLA-DRB103 allele conferring good prognosis. (Note: smoking's inverse epidemiologic association is not a basis for recommending smoking, whose net harms greatly outweigh this signal.)

Gene–environment interactions. The HLA class II genotype shapes which antigenic peptides are presented, effectively determining the response to environmental/microbial triggers. The 8.1 ancestral haplotype (HLA-A01:01∼B08:01∼C07:01∼DRB103:01∼DQA105:01∼DQB102:01) associates with the benign Löfgren phenotype (PMID: 37153085), illustrating how a specific HLA context converts an antigen exposure into a self-limited rather than chronic disease.

3. Phenotypes

Sarcoidosis phenotypes span constitutional symptoms, organ-specific manifestations, and laboratory abnormalities.

Phenotype	Type	Frequency / notes	Suggested HPO term
Pulmonary involvement / interstitial lung disease	Clinical sign	>90%	HP:0002206 (Pulmonary fibrosis)
Bilateral hilar lymphadenopathy	Imaging sign	Common; CT 82.7% vs CXR 29.5% detection ([PMID: 41651390])	HP:0100721 (Hilar lymphadenopathy)
Cough / dyspnea	Symptom	Common	HP:0012735 (Cough); HP:0002094 (Dyspnea)
Fatigue	Symptom	Very common; major QoL driver	HP:0012378 (Fatigue)
Erythema nodosum (part of Löfgren)	Physical manifestation	Acute presentation	HP:0012219 (Erythema nodosum)
Cutaneous sarcoid / lupus pernio	Physical manifestation	~25%	HP:0000951 (Abnormal skin morphology)
Uveitis / ocular sarcoidosis	Clinical sign	Frequent; anterior/intermediate/posterior/panuveitis ([PMID: 42364256])	HP:0000554 (Uveitis)
Cardiac involvement (arrhythmia, cardiomyopathy, sudden death)	Clinical sign	Underrecognized; can be first manifestation ([PMID: 41410048])	HP:0011675 (Arrhythmia)
Neurosarcoidosis (CNS inflammation)	Clinical sign	~5–10%	HP:0002383 (Encephalitis)
Hypercalcemia / hypercalciuria / nephrolithiasis	Lab abnormality	Vitamin D dysregulation; nephrolithiasis OR 1.80 in Black women ([PMID: 41646626])	HP:0003072 (Hypercalcemia)
Elevated serum ACE / sIL-2R	Lab abnormality	Reflects granuloma burden	—
Arthritis (Blau triad)	Clinical sign	Early-onset form	HP:0001369 (Arthritis)

Phenotype characteristics. Age of onset is predominantly adult (30–60 years), with a second peak in women >50; the monogenic Blau form is early childhood-onset. Severity is highly variable (mild/self-limited to severe multiorgan). Progression is episodic or progressive, with two dominant trajectories (Section 8). Frequency among affected individuals is organ-dependent (lung near-universal; cardiac/CNS minority but high-consequence).

Quality of life impact. Ocular sarcoidosis causes major morbidity: one-third of sarcoid uveitis patients develop cataract (35.7%), glaucoma (30.6%), cystoid macular edema (16.1%), and low vision/blindness (10.2%) within 5 years (PMID: 41512253). Fatigue and dyspnea are the dominant patient-reported QoL burdens; efzofitimod trials measured "clinically meaningful improvements... across several patient-reported outcomes" (PMID: 36356657).

4. Genetic / Molecular Information

Causal genes. For classic multifactorial sarcoidosis there is no single causal gene; susceptibility is polygenic. The strongest and best-replicated signals are in the MHC/HLA class II region (HLA-DRB1, HLA-DQB1, HLA-DRA, HLA-DRB5), plus BTNL2 (butyrophilin-like 2), ANXA11 (annexin A11), and NOTCH4 (PMID: 22952805).

For the monogenic Blau syndrome / early-onset sarcoidosis, the causal gene is NOD2 (CARD15) on chromosome 16q12. It is a rare autosomal-dominant granulomatous disease: "Blau syndrome is a rare, autosomal dominant granulomatous disease caused by mutations in the NOD2/CARD15 gene. While the classic triad of arthritis, dermatitis, and uveitis is well known" (PMID: 40667856).

Pathogenic variants (Blau/NOD2).

Variant	Type	Domain	Consequence
R334W	Missense	NBD (nucleotide-binding)	Gain of function / altered signaling
R334Q	Missense	NBD	Gain of function
M513T (de novo reported)	Missense	NBD	Gain of function ([PMID: 36915122])

Mechanistically: "Blau NOD2 mutations precipitate a loss of canonical NOD2 signaling" (PMID: 36189261) and result in loss of NOD2 cross-regulatory function. A T-cell–intrinsic role for NOD2 downstream of TCR signaling has also been proposed (PMID: 40824708). These variants are classified pathogenic / likely pathogenic and are germline.

HGNC IDs (key genes): HLA-DRB1 (HGNC:4948), HLA-DQB1 (HGNC:4944), BTNL2 (HGNC:1142), ANXA11 (HGNC:535), NOTCH4 (HGNC:7884), NOD2 (HGNC:5331).

Modifier genes / prognostic alleles. HLA-DRB1 acts as a major disease-modifier: "Human leukocyte antigen (HLA)-DRB103 is over-represented in LS, and is associated with a good prognosis, whereas HLA-DRB115-positive patients have a more chronic course of sarcoidosis" (PMID: 30585624). In a Czech cohort, HLA-DRB111:01 and DQA105:05 associated with advanced disease, while DRB103:01/DQA105:01 associated with remission (PMID: 37153085). HLA-DRB1*04 correlated with elevated serum ACE and extrapulmonary manifestations (PMID: 39393304).

Epigenetic information & chromosomal abnormalities. No recurrent chromosomal abnormality (aneuploidy, translocation) defines sarcoidosis. Epigenetic contributions (DNA methylation, chromatin changes affecting macrophage polarization) are an active area but were not available at high granularity in this review.

5. Environmental Information

Environmental factors. Microbial bioaerosols and occupational particulate exposures are the best-supported contributors: musty/moldy work environments (OR 1.62) and insecticide exposure (OR 1.61) (PMID: 15347561); WTC dust produced a documented epidemic of sarcoid-like disease (PMID: 21298693).

Lifestyle factors. Cigarette smoking is inversely associated (OR 0.65) (PMID: 15347561). Obesity is a recognized risk factor (PMID: 40002701). Tattoo pigments (especially black ink) can trigger localized granulomatous/uveitic reactions (PMID: 41055154).

Infectious agents. Mycobacterium tuberculosis (NCBITaxon:1773) and Cutibacterium/Propionibacterium acnes (NCBITaxon:1747) are the leading candidate microbial triggers. Mycobacterial antigens (mKatG, ESAT-6, SodA) drive the disease-specific T-cell response (Sections 6/10), and P. acnes is used to induce sarcoid-like granulomas in animal models (PMID: 41933939). Sarcoidosis is not an active infection — cultures are negative — but an immune response to poorly degradable microbial remnants.

6. Mechanism / Pathophysiology

Causal chain (upstream → downstream).

Genetic susceptibility (HLA-DRB1/DQB1, BTNL2, ANXA11, NOTCH4; NOD2 in Blau)
│
▼
Exposure to persistent, poorly degradable antigen
(mycobacterial mKatG / ESAT-6 / SodA; environmental bioaerosols)
│
▼
APC (dendritic cell/macrophage) presents antigen via HLA class II
│
▼
Antigen-specific CD4+ T-cell activation → Th1 (IFN-γ, IL-2) + Th17 (IL-17) skew
│
▼
Macrophage activation & mTORC1 hyperactivation → M1 polarization
│
▼
Epithelioid transformation + multinucleated giant cell formation
│
▼
NONCASEATING GRANULOMA  ──► resolution (≈70%)
│
▼ (persistent antigen / HLA-DRB1*15)
Chronic inflammation → fibroblast activation → FIBROSIS / organ damage

Molecular pathways. The central druggable node is mTORC1. Conditional deletion of Tsc1 or Tsc2 in mice "leads to spontaneous formation of sarcoid-like granulomas, driven by hyperactivation of the mTORC1 pathway in fibroblasts and interstitial macrophages" (PMID: 42246493). mTORC1 regulates the CCL24–CCR3 chemokine axis controlling granuloma formation/maintenance. Additional pathways: NF-κB (downstream of NOD2/RIP2), STAT1 (M1 polarization), STAT3, and JAK-STAT (IFN-γ signaling; rationale for JAK inhibitors). Suggested GO terms: GO:0032008 (positive regulation of TOR signaling); GO:0002548 (monocyte chemotaxis); GO:0042110 (T cell activation); GO:0006954 (inflammatory response).

Cellular processes. Chronic granulomatous inflammation; macrophage M1 polarization; impaired autophagic clearance. Sirolimus data show "aberrant mTORC1 activation promotes macrophage-driven inflammation and disrupts autophagic clearance, sustaining granuloma formation. Sirolimus, a selective mTORC1 inhibitor, restores autophagy and macrophage function" (PMID: 40996589). Legumain (LGMN) restrains granuloma formation by inhibiting mTORC1/STAT1-driven M1 polarization; genetic Lgmn deletion exacerbates granulomatous inflammation (PMID: 41933939). CXCR6 drives Th17 responses; targeting CXCR6 suppresses granuloma formation and pulmonary fibrosis (PMID: 42143504).

Immune system involvement. Sarcoidosis is a CD4+ Th1/Th17-driven disease. The granuloma consists of "monocytes and dendritic cells, macrophages, multinucleated giant cells, and T cells" (PMID: 41410048). Disease-specific CD4+ T cells recognize mycobacterial ESAT-6 and KatG (Section 10). Suggested CL terms: CL:0000624 (CD4+ T cell); CL:0000860 (classical/M1 macrophage); CL:0000451 (dendritic cell).

Protein dysfunction. In Blau syndrome, mutant NOD2 exhibits altered NBD-domain conformation causing dysregulated NF-κB signaling and loss of cross-regulatory function (PMID: 36189261, PMID: 42039171). The candidate antigen mKatG is notably poorly soluble and protease-resistant, explaining persistence (PMID: 15753209).

Metabolic changes. Dysregulated vitamin D metabolism — granuloma macrophages express 1α-hydroxylase, causing extrarenal 1,25-dihydroxyvitamin D production, hypercalcemia, hypercalciuria, and increased nephrolithiasis risk (OR 1.80 in Black women) (PMID: 41646626).

Single-cell / spatial profiling. Single-cell RNA sequencing and spatial transcriptomics have "increased our understanding of disease pathogenesis" (PMID: 41651390). Direct immune mapping compared "the immunological microenvironments of granulomas from TB and sarcoidosis patients" (PMID: 38385142) — sarcoid granulomas are non-necrotizing with a central epithelioid/giant-cell core surrounded by a CD4+ Th1/Th17 cuff, contrasting with the necrotic core of TB granulomas.

7. Anatomical Structures Affected

Organ level. Primary: lungs (UBERON:0002048) and intrathoracic/hilar lymph nodes (UBERON:0000029), affected in >90%. Secondary/other organs: skin (UBERON:0002097), eye/uvea (UBERON:0000970 / UBERON:0001769), heart (UBERON:0000948), CNS/brain (UBERON:0000955), liver (UBERON:0002107), spleen (UBERON:0002106), kidney (UBERON:0002113).

Body systems. Respiratory (primary), lymphatic/immune, integumentary, cardiovascular, nervous, hepatobiliary, ocular/visual, and musculoskeletal.

Tissue and cell level. The affected tissue is the granuloma, composed of epithelioid macrophages (CL:0000860), multinucleated giant cells, dendritic cells (CL:0000451), and a rim of CD4+ T cells (CL:0000624) with Th17 cells; fibroblasts (CL:0000057) drive downstream fibrosis. BAL typically shows lymphocytosis with elevated CD4/CD8 ratio; BALF cell subsets carry prognostic significance (PMID: 34198166).

Subcellular level. Key compartments: lysosome/autophagosome (impaired autophagic clearance; GO:0005764, GO:0005776) and cytosol (NOD2 as cytosolic sensor; GO:0005829).

Localization / lateralization. Pulmonary/lymph node involvement is characteristically bilateral and symmetric (bilateral hilar lymphadenopathy is the radiographic hallmark). Cutaneous and ocular disease may be bilateral or asymmetric.

8. Temporal Development

Onset. Typical onset is adult (30–60), with a female second peak after 50; ocular sarcoidosis most commonly affects adults 30–60 (PMID: 42364256). The monogenic Blau form is early childhood-onset. Onset ranges from acute (Löfgren: fever, erythema nodosum, bilateral hilar lymphadenopathy, arthralgia) to insidious/subacute.

Progression — disease stages. Pulmonary sarcoidosis is graded by the Scadding chest X-ray stages: 0 (normal), I (bilateral hilar lymphadenopathy), II (lymphadenopathy + parenchymal infiltrates), III (infiltrates alone), IV (fibrosis). Higher stage correlates with worse prognosis and elevated ACE (PMID: 39393304).

Disease course. Population-scale trajectory analysis (Swedish register, n=9,665) identified "two distinct trajectories... a resolving trajectory (71.5%) with near-complete remission of sarcoidosis-related visits within two years, and a chronic trajectory (28.5%) with persistently elevated visit rates over five years" (PMID: 42498935). The strongest predictor of chronicity was immunosuppressive treatment around diagnosis (RR 2.18, CI 2.04–2.33), a severity marker.

Patterns. Remission is frequently spontaneous (especially Löfgren / HLA-DRB103). Chronic disease (enriched HLA-DRB115) can be relapsing-remitting or progressive to fibrosis. The critical intervention window is early, before irreversible fibrotic damage.

9. Inheritance and Population

Epidemiology. Prevalence/incidence vary by geography and ancestry. In TriNetX, among 108,597,869 patients, 146,356 had sarcoidosis, with rising prevalence over 12 years (PMID: 41512253). Estimated prevalence is ~10–40 per 100,000 in most Western populations, substantially higher in African Americans (~three-fold).

Inheritance. Classic sarcoidosis is multifactorial/polygenic with familial aggregation but no Mendelian pattern. Blau syndrome is autosomal dominant (NOD2), including de novo mutations (e.g., M513T) (PMID: 36915122). Penetrance and expressivity are variable. Genetic anticipation, germline mosaicism, and founder effects are not established for sarcoidosis.

Population demographics.

Dimension	Finding
Ancestry	Higher prevalence and more severe, chronic, multiorgan disease in African-ancestry individuals
Sex	Female predominance (56.5–60.4% in sarcoid/sarcoid uveitis cohorts) ([PMID: 41512253])
Race (sarcoid uveitis)	Majority Black/African American (43.68%) despite White majority overall ([PMID: 41512253])
Mortality disparity	All-cause mortality 6.4% higher in Black vs White veterans (MRR 1.064; P=0.02) ([PMID: 39521376])
Geographic	Higher incidence in Northern Europe (Scandinavia) and among US African Americans

Mortality trend. In the VHA cohort (n=23,745, 2004–2022), "all-cause mortality increased annually by 4.7% (P < .0001) and was 6.4% higher in Black than White veterans (mortality rate ratio, 1.064; P = .02)" (PMID: 39521376).

10. Diagnostics

Diagnostic principle. Diagnosis is one of exclusion, requiring (1) compatible clinico-radiologic features, (2) biopsy demonstrating noncaseating epithelioid granulomas, and (3) exclusion of infectious and neoplastic mimics (PMID: 41651390, PMID: 42237759).

Laboratory biomarkers — sIL-2R outperforms serum ACE.

Study / cohort	sIL-2R sensitivity	ACE sensitivity	Other
Ocular cohort ([PMID: 33420542])	76.4%	37.7%	KL-6 26.3%, Ca 11.8%
Dermatology cohort ([PMID: 28295528])	52.8%	29%	Lysozyme 26.4%
Suspected-sarcoidosis cohort ([PMID: 31622413])	Sens 88% / Spec 85%	Sens 62% / Spec 76%	sIL-2R superior (p<0.0001)

Verbatim: "The sensitivity for sIL-2R (76.4%) was higher than for ACE (37.7%), KL-6 (26.3%), and Ca (11.8%)" (PMID: 33420542); "sIL-2R was more sensitive than both ACE and lysozyme in supporting a diagnosis of sarcoidosis (52.8%) compared with ACE (29%) and lysozyme (26.4%)" (PMID: 28295528). sIL-2R also predicts EBUS-TBNA diagnostic yield (PMID: 33093764). Additional labs: hypercalcemia/hypercalciuria, elevated CD4/CD8 ratio on BAL. For neurosarcoidosis, ACE is a poor biomarker; candidate markers include sIL-2R, CD4/CD8 ratio, neopterin, IFN-γ, and CCL2 (PMID: 38875863).

Imaging. Contrast chest CT detects bilateral hilar lymphadenopathy far better than plain radiography (82.7% vs 29.5%) (PMID: 41651390). ¹⁸F-FDG PET and cardiac MRI are used for cardiac and occult-organ disease.

Biopsy / histopathology. Gold standard is tissue showing noncaseating epithelioid granulomas with exclusion of infection (special stains/culture negative) and malignancy. EBUS-TBNA combined with transbronchial lung biopsy achieved 100% diagnostic yield in stage I/II disease (PMID: 33093764).

Genetic testing. Not indicated for classic multifactorial sarcoidosis. For suspected Blau syndrome, single-gene or panel sequencing of NOD2 (CARD15) is diagnostic (PMID: 40667856). HLA typing has prognostic (not diagnostic) utility.

Differential diagnosis. Tuberculosis and other infections, lymphoma/malignancy, hypersensitivity pneumonitis, berylliosis, and sarcoid-like reactions (SLR) triggered by drugs (e.g., dupilumab, checkpoint inhibitors), malignancy, or infection (PMID: 42237759, PMID: 42126659). Immune mapping distinguishes sarcoid from TB granulomas (PMID: 38385142).

11. Outcome / Prognosis

Course & remission. Prognosis is bimodal: ~71.5% resolve within 2 years, ~28.5% become chronic (PMID: 42498935). Löfgren syndrome (HLA-DRB103) carries an excellent prognosis; HLA-DRB115 predicts chronicity (PMID: 30585624).

Mortality. Sarcoidosis mortality is rising (annual increase 4.7%) with persistent Black-vs-White disparity (MRR 1.064) (PMID: 39521376). Leading causes of death: progressive pulmonary fibrosis/respiratory failure, cardiac sarcoidosis (arrhythmia, sudden death), and pulmonary hypertension (PMID: 41410048).

Morbidity & complications. Pulmonary fibrosis; cardiac arrhythmia and sudden death (can be the initial manifestation) (PMID: 41410048); neurosarcoidosis; ocular complications (cataract 35.7%, glaucoma 30.6%, blindness 10.2%) (PMID: 41512253); nephrolithiasis (PMID: 41646626); chronic fatigue.

Prognostic factors. Favorable: acute Löfgren onset, HLA-DRB103, low Scadding stage, normal ACE. Unfavorable: HLA-DRB115/11:01, elevated ACE with extrapulmonary manifestations (PMID: 39393304), African ancestry, cardiac/CNS involvement, higher BALF lymphocyte/neutrophil/eosinophil counts (PMID: 34198166), and need for early immunosuppression (RR 2.18 for chronicity) (PMID: 42498935).

12. Treatment

Not all patients require treatment — many self-limited cases are observed. For those needing therapy, escalation is stepwise.

Pharmacotherapy.

Line	Agent(s)	Class / mechanism	MAXO suggestion
First	Corticosteroids (prednisone)	Broad immunosuppression	MAXO:0000305 (corticosteroid therapy)
Second (steroid-sparing)	Methotrexate	Antimetabolite / antifolate	MAXO:0000916 (methotrexate therapy)
Second	Azathioprine, leflunomide	Immunosuppressants	MAXO (immunosuppressant therapy)
Refractory	Infliximab (anti-TNF-α mAb)	TNF-α neutralization	MAXO (biologic/anti-TNF therapy)

"Corticosteroids remain the initial drug for most patients... Methotrexate is [the] most commonly used cytotoxic agent used for chronic disease, but azathioprine and leflunomide also have been shown to be useful. The tumor necrosis factor antibody infliximab has proved useful in treating refractory sarcoidosis" (PMID: 18539243).

Emerging / targeted therapeutics.

Efzofitimod (ATYR1923) — first-in-class neuropilin-2–binding immunomodulator. In a randomized, double-blind, placebo-controlled phase 1b/2a trial (n=37, IV q4w × 24 weeks with forced steroid taper), it was well tolerated and produced "a baseline-adjusted relative steroid reduction of 5%, 9%, and 22%, respectively. Clinically meaningful improvements were achieved across several patient-reported outcomes, several of which reached statistical significance in the 5 mg/kg dose arm" (PMID: 36356657). Mechanism: "Efzofitimod (ATYR1923), a novel immunomodulator, selectively binds neuropilin 2, which is upregulated on immune cells in response to lung inflammation."
mTOR inhibitors (sirolimus) — effective in refractory multisystem sarcoidosis by restoring autophagy/macrophage function (PMID: 40996589).
JAK inhibitors and IL-6 receptor antagonists — promising for refractory sarcoid uveitis on top of methotrexate/TNF inhibitors (PMID: 42364256).
Preclinical targets: CXCR6 blockade (PMID: 42143504); LGMN supplementation (PMID: 41933939).

Blau syndrome-specific. TNF-α inhibitors are effective for ocular/joint disease (PMID: 40667856).

Pharmacogenomics. No sarcoidosis-specific PGx dosing is established; standard TPMT/NUDT15 testing applies before azathioprine.

13. Prevention

Primary prevention. No vaccine or proven primary-prevention strategy exists. Given occupational associations, reducing bioaerosol/mold and insecticide exposures is rational but unproven (PMID: 15347561).

Secondary prevention. Early detection of high-consequence organ involvement — particularly cardiac screening (ECG/echo) in newly diagnosed patients — can prevent sudden cardiac death (PMID: 41410048). Pulmonology/sarcoidosis-clinic referral is associated with recommended cardiopulmonary screening, yet sociodemographic disparities exist (Black males and White females less likely to be referred) (PMID: 40890688).

Tertiary prevention. Early steroid-sparing therapy to prevent corticosteroid toxicity and irreversible fibrosis; monitoring for vitamin D/calcium dysregulation and nephrolithiasis, especially with metabolic comorbidities (PMID: 41646626).

Counseling. Genetic counseling is relevant for Blau syndrome (autosomal dominant, NOD2). No population carrier screening applies to classic sarcoidosis.

14. Other Species / Natural Disease

Taxonomy. Sarcoidosis is essentially a human disease (Homo sapiens, NCBITaxon:9606). No true naturally occurring idiopathic analog is established in companion animals or wildlife; granulomatous diseases in other species (e.g., mycobacterial granulomas) share cellular architecture but are typically infectious.

Orthologous genes. Key genes have clear orthologs used in modeling: mouse Nod2 (NCBI Gene 257632), Tsc1/Tsc2, Lgmn, Cxcr6. The granuloma is an evolutionarily conserved host-defense structure, leveraged in comparative TB-vs-sarcoidosis immune mapping (PMID: 38385142).

Transmission / zoonotic potential. Sarcoidosis is not transmissible and has no zoonotic potential; the mycobacterial-antigen hypothesis concerns immune reactivity to microbial remnants, not active/contagious infection.

15. Model Organisms

Mammalian genetic models.

Model	Design	Phenotype recapitulation
Fsp1-Cre; Tsc1^fl/fl or Tsc2^fl/fl mouse	Conditional deletion in fibroblasts/macrophages	Spontaneous sarcoid-like granulomas via mTORC1 hyperactivation ([PMID: 42246493])
Lgmn^-/- mouse (P. acnes-induced)	Knockout + microbial induction	Exacerbated granulomatous inflammation, increased M1 polarization ([PMID: 41933939])
CXCR6-targeted mouse	Pathway inhibition	Reduced granuloma + fibrosis via Th17 suppression ([PMID: 42143504])

Induced (non-genetic) models. Propionibacterium acnes- and trehalose-6,6′-dimycolate (cord factor)-induced pulmonary granuloma models reproduce granuloma formation and are used to test therapeutics (PMID: 41933939).

Applications & limitations. These models recapitulate granuloma formation, macrophage polarization, and the mTORC1/STAT1 axis, enabling target validation (mTOR inhibitors, LGMN, CXCR6). Limitations: they do not fully capture the human HLA-restricted antigen-specific CD4+ response, the bimodal natural history, or multiorgan heterogeneity. Cellular/in vitro systems (patient BAL T cells, monocyte-derived macrophages) complement in vivo models. Resources: MGI (mouse); Alliance of Genome Resources.

Mechanistic Model / Interpretation

Sarcoidosis is best understood as a three-hit convergence: (1) a permissive HLA class II genotype, (2) exposure to a persistent, poorly degradable antigen, and (3) a resulting self-amplifying CD4+ Th1/Th17 granulomatous response in which mTORC1 hyperactivation locks macrophages into a granuloma-forming, autophagy-impaired state. The HLA allele determines fate: DRB103 contexts (Löfgren) tend to clear the antigen and resolve, whereas DRB115/11:01 contexts sustain the response toward chronic fibrosis. The "missing antigen" is increasingly resolved toward mycobacterial remnants (mKatG, ESAT-6, SodA), recognized by lung-compartmentalized CD4+ T cells in most patients but rarely controls. This model unifies the genetics (HLA/BTNL2/ANXA11/NOTCH4), the environmental epidemiology (bioaerosols, WTC dust), the monogenic mirror (NOD2/Blau — a pure innate-sensing lesion producing the same granuloma), the therapeutic response (mTOR inhibition, anti-TNF, NRP2 modulation), and prognostic stratification.

Evidence Base (Key Literature)

PMID	Contribution
22952805	GWAS: HLA-DRA/DRB5/DRB1, BTNL2, ANXA11, independent NOTCH4 susceptibility
15347561 / 17684288	ACCESS: environmental/occupational risk and inverse smoking association
42246493 / 40996589 / 41933939	mTORC1 as causal, druggable granuloma driver; sirolimus efficacy; LGMN restraint
30585624 / 37153085 / 42498935	HLA-DRB1 prognostic alleles; bimodal natural history (71.5% resolve)
33420542 / 28295528 / 31622413 / 41651390	sIL-2R > ACE; diagnosis of exclusion with granuloma histology
40667856 / 36189261 / 36915122	Blau syndrome: AD NOD2 disease, mechanism, variants
38385142 / 41651390	Single-cell/spatial mapping distinguishing sarcoid vs TB granulomas
36356657	Efzofitimod (NRP2 immunomodulator) steroid-sparing phase 1b/2a
39521376	Rising mortality with Black-vs-White disparity
15753209 / 19596780 / 19050300 / 17924974	Mycobacterial mKatG/ESAT-6/SodA as candidate pathogenic antigens

Selected verbatim support for the antigen hypothesis: "Matrix-assisted laser desorption/ionization time of flight mass spectrometry identified Mycobacterium tuberculosis catalase-peroxidase (mKatG) as one of these tissue antigens" (PMID: 15753209); and "the presence of antigen-specific recognition of ESAT-6 and KatG in T cells from BAL fluid of 32/44 sarcoidosis subjects, compared to 1/27 controls (P < 0.0001)" (PMID: 19596780).

Limitations and Knowledge Gaps

Etiology remains formally unproven. Despite strong immunological evidence for mycobacterial antigens, sarcoidosis is not an active infection, and no single agent satisfies Koch-style criteria. mKatG reactivity is present in ~55–73% of patients — not all.
Missing data domains. Detailed epigenetic profiling, comprehensive proteomic/metabolomic/lipidomic signatures, and precise population incidence figures were not resolved at high granularity in this investigation.
Model organism gap. Available mouse models capture granuloma biology but not the HLA-restricted antigen-specific human response or the bimodal natural history.
Biomarker limitations. sIL-2R and ACE both lack organ specificity (particularly poor for neurosarcoidosis); no validated biomarker reliably predicts chronicity prospectively.
Therapeutic evidence. Efzofitimod and sirolimus data derive from small/early-phase or case-series studies; large confirmatory RCTs are pending.
No primary-data hypothesis tests were run in this investigation; conclusions rest on literature synthesis of published cohorts.

Proposed Follow-up Experiments / Actions

Prospective HLA + antigen-reactivity stratification: combine HLA-DRB1 typing with BAL T-cell mKatG/ESAT-6 ELISPOT at diagnosis to predict resolving vs chronic trajectory.
mTORC1 biomarker + trial: validate phospho-S6/phospho-STAT1 in granuloma macrophages as a companion biomarker for a randomized sirolimus (or JAK-inhibitor) trial in refractory disease.
Confirmatory efzofitimod RCT analysis with organ-specific and QoL endpoints; correlate response with baseline NRP2 expression.
Single-cell/spatial atlas across trajectories: contrast resolving vs chronic granulomas to identify fibroblast/macrophage programs driving fibrosis and candidate anti-fibrotic targets (e.g., CXCR6).
Disparity-focused implementation study: address referral and mortality disparities in Black patients through targeted care-pathway interventions.
NOD2/Blau mechanistic bridge: test whether NOD2 gain-of-function and mycobacterial-driven classic sarcoidosis converge on a shared mTORC1/NF-κB macrophage program, potentially unifying monogenic and multifactorial forms.

Report compiled from 44 reviewed papers and 10 confirmed findings across 5 investigation iterations. Evidence source types span human clinical cohorts (GWAS, registries, case-control), model organism (conditional-knockout mice), in vitro (patient BAL/PBMC T cells), and computational/single-cell profiling.

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Inheritance

Subtypes

Mechanistic Hypotheses

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Environmental Factors

Biochemical Markers

Source YAML

References & Deep Research

Deep Research

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic / Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome / Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Suggested dismech modeling anchors

Key References (verify all before committing)

1. Disease Information

1.1 Definition and overview

1.2 Key identifiers (with availability in retrieved sources)

1.3 Synonyms / alternative names

1.4 Evidence provenance

2. Etiology

2.1 Causal factors (current consensus)

2.2 Genetic risk factors (susceptibility/severity loci)

2.3 Environmental and infectious risk factors

2.4 Protective factors

2.5 Gene–environment interactions

3. Phenotypes (clinical manifestations)

3.1 Core clinical phenotype domain

3.2 Example organ involvement frequencies (from retrieved sources)

3.3 Onset and course (high-level)

3.4 Quality of life

3.5 HPO term suggestions (non-exhaustive; mapped to retrieved phenotype domains)

4. Genetic/Molecular Information

4.1 “Causal genes” vs susceptibility genes

4.2 Pathogenic variants (status in retrieved evidence)

4.3 Modifier genes / severity genetics

4.4 Epigenetic information

5. Environmental Information

6. Mechanism / Pathophysiology

6.1 Causal chain (trigger → granuloma → organ dysfunction)

6.2 Key immune pathways and cell types (with ontology suggestions)

6.3 Recent developments (2023–2024 priority): single-cell / spatial / metabolic mechanisms

6.4 Imaging/biopsy advances linked to mechanism

7. Anatomical Structures Affected

7.1 Organ-level involvement

7.2 UBERON suggestions (non-exhaustive)

8. Temporal Development

9. Inheritance and Population

9.1 Epidemiology (incidence, prevalence, demographics)

9.2 Genetic architecture / inheritance

10. Diagnostics

10.1 Diagnostic criteria (core consensus)

10.2 Histopathology

10.3 Laboratory tests / biomarkers

10.4 Imaging

10.5 Differential diagnosis

11. Outcome / Prognosis

11.1 Mortality and survival (recent real-world estimates)

11.2 Prognostic functional markers

12. Treatment

12.1 Current standard pharmacotherapy (guideline-aligned approach)

12.2 Recent developments (high-priority evidence)