Lymphomatoid Granulomatosis: Comprehensive Research Report

1. Disease Information

Overview. Lymphomatoid granulomatosis (LYG) is a rare, Epstein-Barr virus (EBV)–driven, angiocentric and angiodestructive B-cell lymphoproliferative disease that arises against a background of defective host immune surveillance of EBV. First described by Averill Liebow in 1972, it is now recognized in the WHO classification as a distinct entity most closely related to a T-cell/histiocyte-rich large B-cell lymphoma variant, formally classified since 2015 within the WHO Classification of Tumours of the Lung, Pleura, Thymus and Heart, and retained in the 2016/2022 WHO classifications of mature lymphoid neoplasms (Melani et al., Blood 2020, PMID 32107539; PathologyOutlines). Histologically it is defined by an angiocentric, angioinvasive, extranodal, polymorphous lymphoid infiltrate containing variable numbers of large, atypical, EBV-positive B cells set in a dense background of reactive, predominantly CD4+ T lymphocytes, with associated coagulative ("tumor") necrosis (PMID 25321327).

Key identifiers: - MONDO: MONDO:0019466 - Orphanet: ORPHA:86869 - ICD-10-CM: C83.8 (Other non-follicular lymphoma) - ICD-O: 9766/1 - OMIM: No dedicated single-gene OMIM entry exists for sporadic LYG (it is not a classic monogenic Mendelian disorder); related immunodeficiency-associated lymphoproliferative OMIM entries exist for specific germline predisposition syndromes (e.g., OMIM #613011, Lymphoproliferative syndrome 1)

Synonyms: angiocentric immunoproliferative lesion (AIL); "LG"/"LYG"; historically grouped with (though not identical to) polymorphic reticulosis/lethal midline granuloma and angiocentric lymphoma under the older umbrella term "angiocentric immunoproliferative lesions," though modern classification distinguishes LYG (B-cell driven, EBV+, multi-organ) from nasal NK/T-cell lymphoma (formerly "polymorphic reticulosis") (GARD; PMID 7281476).

Evidence basis: Information is derived almost entirely from aggregated case series, single-institution retrospective cohorts, and one prospective NCI phase 2 interventional trial — not large-scale EHR/claims data — reflecting the disease's rarity.

2. Etiology

Primary causal driver — EBV plus host immune dysfunction. LYG is hypothesized to result from defective cell-mediated immune surveillance of EBV-infected B cells, permitting outgrowth of EBV-driven B-cell clones amid a robust but ineffective reactive T-cell response ("hyperimmune" reaction), rather than from any single germline oncogenic driver (PMID 32107539). A functional defect, primarily in CD8+ cytotoxic T-cell immunosurveillance, is hypothesized as a prerequisite; notably, the reactive infiltrate itself is CD4-predominant (CD4:CD8 ratio favoring CD4 in 95% of cases, 20/21) rather than CD8-predominant, consistent with an ineffective/dysregulated rather than absent T-cell response (PMID 25321327).

Genetic/immunologic risk factors: - Underlying primary or acquired immunodeficiency is documented in a substantial fraction of cases even without a formally diagnosed syndrome. Recognized associated conditions include: - Wiskott–Aldrich syndrome (X-linked; marked predisposition to EBV-associated lymphoma) - X-linked lymphoproliferative syndrome (XLP) - Common variable immunodeficiency (CVID) - DOCK8 deficiency — a combined immunodeficiency in the hyper-IgE spectrum; a 2017 report described EBV+ LYG as a previously unreported presentation of DOCK8 deficiency, with resolution of LYG following hematopoietic stem cell transplantation in affected relatives (PMID from Frontiers report, DOCK8/LYG) - HIV/AIDS — via CD4+ T-cell depletion and loss of EBV control - Solid organ transplantation (iatrogenic immunosuppression) — placing LYG within the broader post-transplant lymphoproliferative disease (PTLD) spectrum in transplant recipients - No recurrent chromosomal abnormalities have been reported in LYG, and no single causal driver gene/variant analogous to a classic Mendelian mutation has been established (PMID 32107539). - Sporadic disease without recognized immunodeficiency is also common — most affected adults have no formally diagnosed primary immunodeficiency syndrome, suggesting a subtler or acquired immune surveillance defect specific to EBV.

Environmental/infectious factor — EBV is central and essentially obligate. EBV (a γ-herpesvirus) genomes and gene products (EBER, LMP1) are demonstrable in the neoplastic B cells of the great majority of cases across grades (EBER positivity: ~46% in grade 1, 100% in grade 2, 94% in grade 3 lesions per PMID 25321327), supporting EBV as the direct causal/transforming agent rather than a bystander.

Protective factors: No specific genetic or environmental protective factor has been established in the literature; intact cell-mediated (particularly CD8+ cytotoxic T-lymphocyte) immunosurveillance of EBV is implicitly protective, as evidenced by disease remission following immune reconstitution (e.g., antiretroviral therapy in newly diagnosed HIV, or reduction of immunosuppression in transplant recipients) (PMC11829542).

Gene-environment interaction: The disease represents a paradigmatic gene(immune)-environment(EBV) interaction: a host with a quantitative or qualitative T-cell surveillance defect (genetic/immunodeficiency-related or acquired) fails to control EBV-driven B-cell proliferation, and progressive genetic/clonal evolution of the EBV+ B-cell population (increasing clonality with grade) leads to transformation toward overt lymphoma.

3. Phenotypes

LYG is multisystemic, with organ involvement documented in a 55-patient single-institution series (Song et al., Am J Surg Pathol 2015, PMID 25321327):

Pulmonary phenotype (near-universal, ~90–100% of cases): Presenting symptoms include cough, dyspnea, chest pain, and fever; imaging shows bilateral, peribronchovascular, lower/peripheral-lung-predominant nodules or masses in 80–100% of cases, with cavitation, small thin-walled cysts, atelectasis/lobar obstruction, and occasional pneumothorax (AJR, PMID 11044036).

Cutaneous phenotype (~17–55%; second most common site): Multiple erythematous dermal papules and/or subcutaneous nodules, plaques, or a patchy erythematous rash, with ulceration in up to ~30% of affected patients; distribution favors extremities over head/neck (only ~10% head/neck) (Dermatology Advisor; PMC6110445).

CNS phenotype (20–38%): Parenchymal brain lesions, cranial neuropathies, seizures, and focal neurologic deficits; CT shows high-density lesions. CNS involvement is a major adverse prognostic factor — one CNS-focused cohort reported overall mortality of 63.5% in LYG generally versus 86.0% in CNS-LYG specifically, with 5-year mortality of 38–88% and median survival 14–72 months in CNS-involved disease (PMC7516720).

Hepatic and renal phenotype: Often asymptomatic or detected on imaging/labs; renal involvement can present with hematuria or renal impairment without overt vasculitic glomerulonephritis (distinguishing it from ANCA-associated vasculitis).

Constitutional/laboratory phenotypes: Fever, weight loss, malaise; laboratory abnormalities may include cytopenias, and rare cases present with hemophagocytic lymphohistiocytosis (HLH) as an initial manifestation (Frontiers, PMC) or paraneoplastic polymyositis (PMC4757691).

Onset/course: Typically insidious onset in adults (fourth–sixth decade), though a chronic, indolent ("smoldering") cutaneous-only course has also been reported (PMC8841505); grade generally correlates with disease pace, with low-grade disease often smoldering/relapsing-remitting and high-grade disease behaving as an aggressive lymphoma.

Quality of life impact: Not systematically studied via standardized instruments (EQ-5D/SF-36) in this rare disease; qualitatively, pulmonary and CNS involvement drive the greatest functional morbidity.

4. Genetic/Molecular Information

Causal genes: No single germline causal gene for sporadic LYG exists; it is not a classic monogenic disorder. However, LYG has been reported as a rare secondary manifestation of several germline primary immunodeficiency genes: - DOCK8 (hgnc:19191) — autosomal recessive combined immunodeficiency (hyper-IgE syndrome spectrum); reported cause of EBV+ LYG with intrafamilial phenotypic variation (PMC5328973) - WAS — Wiskott-Aldrich syndrome gene, X-linked - Genes underlying XLP (SH2D1A, XIAP) and CVID

Somatic/molecular features of the neoplastic clone: - Clonality: Immunoglobulin heavy-chain gene rearrangement studies show grade-dependent clonality — grade 1: ~8% clonal (1/12); grade 2: ~50% clonal (4/8); grade 3: ~69% clonal (11/16) — consistent with progressive selection/transformation of an EBV-infected B-cell clone with increasing grade (Song et al. 2015, PMID 25321327). - No recurrent cytogenetic abnormalities (translocations, aneuploidy) have been established, unlike most other B-cell lymphomas (PMID 32107539). - EBV gene expression: Neoplastic B cells express EBER (EBV-encoded small RNA, detected by in situ hybridization) and latent membrane protein 1 (LMP1) by immunohistochemistry, consistent with a latency II/III-like expression program; EBER positivity rises from ~46% (grade 1) to 100% (grade 2) to 94% (grade 3) (PMID 25321327). - Immunophenotype of neoplastic cells: CD20+, CD45+, LMP1+ large atypical B cells; background reactive infiltrate is CD3+ T cells, CD4-predominant in 95% of cases (20/21) (PMID 25321327).

Variant classification/allele frequency: Not applicable in the classic ClinVar/gnomAD sense for sporadic LYG, since it is a somatic/EBV-driven lymphoproliferation rather than a germline variant-caused disease; where associated germline immunodeficiency genes (DOCK8, WAS) are implicated, standard ACMG/AMP pathogenic-variant classification applies to those underlying conditions rather than to LYG itself.

Epigenetics: No LYG-specific DNA methylation/histone-modification studies were identified in the search; EBV latency programs themselves involve epigenetic (CpG methylation, histone) regulation of the viral genome, a mechanism general to EBV-associated lymphoproliferations.

5. Environmental Information

Infectious trigger — EBV (Epstein-Barr virus, human gammaherpesvirus 4; NCBITaxon:10376): The central and essentially obligate etiologic agent; EBV genomes are detectable by PCR/in situ hybridization in the overwhelming majority of cases (PMID 2170969).

Iatrogenic/exposure factors: - Immunosuppressive medication — solid organ transplantation, TNF-α inhibitor therapy (a 2023 case report describes pulmonary LYG in a patient on long-term TNF-α inhibitor use, PMID 37160375), and other immunosuppressive regimens for autoimmune disease can precipitate LYG by impairing EBV surveillance. - HIV infection — a well-documented environmental/infectious risk factor via CD4+ T-cell depletion; case reports document LYG remission after immune reconstitution with antiretroviral therapy.

Lifestyle factors: No specific lifestyle risk factor (smoking, diet, alcohol) has been established in the literature as a driver of LYG.

6. Mechanism / Pathophysiology

Causal chain (upstream → downstream): 1. Trigger: EBV infection of B lymphocytes (nearly universal in the population; EBV seroprevalence >90% in adults) combined with a host defect in cell-mediated EBV immunosurveillance (constitutional immunodeficiency, HIV, iatrogenic immunosuppression, or an unidentified subtler defect). 2. Molecular/cellular consequence: Failure of cytotoxic (largely CD8+) T-cell control permits outgrowth of EBV-infected B cells expressing latent viral oncoproteins (LMP1, EBNA), which drive B-cell proliferation and survival signaling (NF-κB activation downstream of LMP1, analogous to other EBV+ lymphoproliferations). 3. Tissue-level consequence: A robust reactive, predominantly CD4+ T-cell response is recruited but is immunologically ineffective at eliminating the EBV+ B-cell population; the mixed infiltrate shows a striking tropism for blood vessel walls (angiocentricity) and vessel destruction (angioinvasion/angiodestruction), producing ischemic coagulative ("tumor") necrosis in affected tissue. 4. Organism-level consequence: Multi-organ tissue destruction (lung nodules/cavitation, cutaneous ulceration, CNS lesions, hepatic/renal involvement) and, with clonal evolution/selection of the EBV+ B-cell population (rising Ig-clonality across grades 1→3), progression from a polyclonal/oligoclonal low-grade lymphoproliferation to a clonal, aggressive B-cell lymphoma indistinguishable from EBV+ diffuse large B-cell lymphoma at grade 3.

Cellular processes involved: Chronic inflammation, angiocentric/angiodestructive vasculopathy (not a true vasculitis, since there is no primary destruction of the vessel wall by an immune-mediated vasculitic process — vessel damage is secondary to lymphocytic infiltration), ischemic/coagulative necrosis, and B-cell clonal selection/malignant transformation.

Grading as a mechanistic readout: The three-tier histologic grading system directly operationalizes the pathobiology — grade is defined by the number/density of large EBV+ B cells and extent of necrosis: - Grade 1: Polymorphous infiltrate, few/no large atypical cells, scant EBV+ B cells (EBER+ ~46%), no or minimal necrosis, low/no clonality (8% clonal) — indolent, "immune-dependent" biology. - Grade 2: Increased large EBV+ B cells (EBER+ 100%), more necrosis, intermediate clonality (50%). - Grade 3: Sheets of large atypical EBV+ B cells resembling conventional EBV+ diffuse large B-cell lymphoma, extensive necrosis, high clonality (69%) — "immune-independent," frankly malignant biology (PMID 25321327; Nakamura/Nature Modern Pathology review).

This grade-dependent biology is the direct rationale for the NCI's differentiated treatment strategy (immunotherapy for immune-dependent low-grade disease vs. cytotoxic chemoimmunotherapy for immune-independent high-grade disease — see Treatment section).

Suggested GO terms: GO:0006955 (immune response), GO:0002432 (granuloma formation), GO:0031295 (T cell costimulation) [context], GO:0043065 (positive regulation of apoptotic process) [reactive T cell attack on infected cells], GO:0001525 (angiogenesis)/GO:0032102 (negative regulation of response to wounding) not directly established. Suggested CL terms: CL:0000236 (B cell) — specifically EBV-transformed large B cell; CL:0000624 (CD4-positive, alpha-beta T cell) for the reactive infiltrate; CL:0000625 (CD8-positive, alpha-beta T cell) for the hypothesized deficient surveillance population.

Advanced/omics profiling: No large-scale transcriptomic, proteomic, single-cell, or spatial transcriptomic dataset specific to LYG was identified in this search — consistent with its rarity and the field's reliance on immunohistochemistry/ISH-based diagnostic pathology rather than genomic profiling to date. This represents a knowledge gap relative to better-characterized B-cell lymphomas.

7. Anatomical Structures Affected

• Primary organ: Lung (near-universal, ~90–100%) — UBERON:0002048 (lung); peribronchovascular/perivascular distribution.
• Secondary/frequently involved organs: Skin (UBERON:0002097, integument), CNS/brain (UBERON:0000955), liver (UBERON:0002107), kidney (UBERON:0002113).
• Body systems: Respiratory, integumentary, nervous, hepatobiliary, renal — a genuinely multisystem disease; lymph nodes and spleen may be secondarily involved (splenomegaly reported, PMC6000673) but are not primary sites (an important distinguishing feature from typical nodal lymphomas).
• Tissue level: Perivascular/angiocentric lymphoid infiltrate within pulmonary interstitium, dermis/subcutis, cerebral parenchyma; vascular smooth muscle and endothelium (targets of angioinvasion).
• Cell populations: Large atypical EBV+ B cells (CD20+, CD45+, LMP1+, EBER+) — Cell Ontology CL:0000236 specialization; reactive CD4+ T cells (CL:0000624) as the dominant background population; histiocytes/plasma cells as minor infiltrate components.
• Subcellular: No specific organelle-level pathology reported (this is not a classic metabolic/storage disease); relevant GO Cellular Component context would be nuclear (EBER, an RNA Pol III transcript, localizes to the nucleus) for viral gene products.
• Localization/laterality: Pulmonary disease is characteristically bilateral; skin lesions favor extremities (bilateral, non-lateralized); CNS lesions can be single or multifocal, no strict laterality pattern reported.

8. Temporal Development

• Onset: Typically adult-onset, fourth to sixth decade of life, though reported across the age spectrum including pediatric cases (children with LYG have been described, including as a rare complication after chemotherapy for pediatric AML, PMID 12571471, and as a cerebellar-mass presentation, AJNR 2007).
• Onset pattern: Usually insidious/subacute; can present acutely in the context of superimposed immunosuppression (e.g., post-transplant, HIV seroconversion).
• Staging/grading as a temporal-progression proxy: Grade 1↔2↔3 functions partly as a progression axis — low-grade disease can progress to high-grade disease over time if untreated or under continued immune impairment, motivating the rationale for early immunotherapy in low-grade disease to forestall transformation (Lancet Haematol 2023, PMID 37011643).
• Progression rate/course pattern: Variable — ranges from an indolent, smoldering, relapsing-remitting cutaneous-limited course (PMC8841505) to a rapidly progressive, aggressive high-grade lymphoma course.
• Remission patterns: Both spontaneous remission (rare, reported with immune reconstitution, e.g., post-antiretroviral therapy in HIV) and treatment-induced remission (interferon-alfa-2b for low-grade disease; DA-EPOCH-R for high-grade) are documented.
• Historical natural history (untreated/steroid-treated): Median survival ~14 months, with 5-year mortality ~50% in older literature predating modern grade-stratified therapy.

9. Inheritance and Population

Epidemiology: - LYG is an exceedingly rare disease of unknown precise population prevalence/incidence — described as "a disease of unknown prevalence" with no dedicated national registry figures identified. - Sex ratio: Male predominance, approximately 2:1 male:female. - Age distribution: Most common in the fourth to sixth decades of adult life; can occur at any age, including rare pediatric cases. - Race/ethnicity: No known racial predilection reported.

Inheritance pattern: LYG itself is not inherited in a classic Mendelian sense — it is a sporadic, EBV-driven lymphoproliferation. However, when it arises secondary to a germline primary immunodeficiency (e.g., DOCK8 deficiency — autosomal recessive; Wiskott-Aldrich syndrome — X-linked recessive), the underlying predisposing condition follows that syndrome's inheritance pattern, and intrafamilial variation in LYG presentation among relatives sharing the same germline DOCK8 mutation has been documented (PMC5328973).

Penetrance/expressivity: Not classically applicable, given the sporadic/acquired nature of most cases; where a germline immunodeficiency is causal, penetrance for LYG specifically (versus other EBV-driven manifestations) is incomplete and variable even within families.

Founder effects/consanguinity/carrier frequency: Not established for LYG itself, though relevant to the rare recessive immunodeficiency syndromes (e.g., DOCK8 deficiency) that can predispose to it.

10. Diagnostics

Tissue diagnosis is required and central. Definitive diagnosis requires tissue biopsy (open lung biopsy or video-assisted thoracoscopic surgery [VATS] for pulmonary disease, or biopsy of an accessible extrapulmonary site such as skin) demonstrating the characteristic angiocentric/angioinvasive polymorphous infiltrate with EBV+ atypical B cells (emedicine Workup).

Ancillary pathology studies: - In situ hybridization for EBER (EBV-encoded RNA) — the key diagnostic test confirming EBV positivity in the atypical B-cell population. - Immunohistochemistry: CD20 (neoplastic B cells), CD3/CD4/CD8 (background reactive T cells, CD4-predominant), LMP1 (latent EBV protein). - Molecular clonality studies: Immunoglobulin heavy-chain gene rearrangement (PCR-based) to assess clonality, correlating with grade.

Imaging: - Chest CT — bilateral, peribronchovascular, lower/peripheral-lung nodules or masses, sometimes with cavitation; the primary modality for detecting and monitoring pulmonary disease. - Brain MRI/CT — for suspected CNS involvement; CT shows high-density lesions. - F18-FDG PET/CT — used to assess multisystem disease distribution, guide high-yield biopsy site selection, and monitor treatment response.

Laboratory studies: No LYG-specific serum biomarker exists; EBV serology/PCR (plasma EBV DNA load) may support the diagnosis and can be used for monitoring, though it is not diagnostic in isolation given high background EBV seroprevalence.

Genetic testing: Not part of routine LYG diagnostic workup unless an underlying primary immunodeficiency is clinically suspected (e.g., recurrent infections, eczema, and elevated IgE suggesting DOCK8 deficiency; recurrent infections/thrombocytopenia/eczema suggesting Wiskott-Aldrich syndrome), in which case targeted gene panel or exome sequencing for primary immunodeficiency genes would be pursued.

Differential diagnosis: - Granulomatosis with polyangiitis (GPA/Wegener's) — distinguished by true necrotizing vasculitis (destruction of the vessel wall itself by the inflammatory process) and typically ANCA positivity, versus LYG's angiocentric/angioinvasive-but-not-classically-vasculitic pattern and EBV positivity. - Sarcoidosis / necrotizing sarcoid granulomatosis — distinguished by well-formed granulomas with giant cells, more frequent mediastinal adenopathy, and absence of EBV+ atypical B cells (LYG characteristically lacks well-formed granulomas or multinucleated giant cells). - Other entities in the differential: pseudolymphoma, other malignant lymphomas (including EBV+ diffuse large B-cell lymphoma, into which grade 3 LYG merges diagnostically), lymphocytic interstitial pneumonia, metastatic disease, cryptogenic organizing pneumonia, infectious granulomatous disease (fungal, mycobacterial).

Screening: No population-level screening program exists given the disease's rarity and lack of an identifiable pre-symptomatic screening marker; surveillance in known immunodeficiency syndromes (DOCK8 deficiency, Wiskott-Aldrich) for EBV-driven lymphoproliferative complications is a reasonable clinical practice, though not formally codified as LYG-specific screening.

11. Outcome/Prognosis

Historical (pre-risk-stratified-therapy) outcomes: Median overall survival was poor, historically cited as 14 months (steroid/chemotherapy era) to under 2 years, with 5-year mortality around 50%.

Modern, grade-stratified therapy outcomes (NCI phase 2 trial, Lancet Haematology 2023, PMID 37011643): - Patients with low-grade disease treated with interferon alfa-2b achieved a median overall survival of approximately 20 years — a dramatic improvement over historical controls. - Progression-free survival for grades 1–2 treated with interferon-alfa was 56%, with median PFS of 5.1 years; for grade 3 treated with DA-EPOCH-R, PFS was 44%, median 32 months (PMID 25321327 reporting NCI cohort outcomes). - Complete response rates in the phase 2 trial: 61% (27/44) after initial interferon alfa-2b in low-grade disease; 47% (8/17) after initial DA-EPOCH-R in high-grade disease; with additional responses after cross-over treatment. - Serious adverse events occurred in about 25% of interferon alfa-2b-treated patients versus nearly two-thirds of chemotherapy-treated patients, favoring the tolerability of immunotherapy for low-grade disease.

Prognostic factors: - Histologic grade is the single most important prognostic factor — grade 3 (high-grade) disease behaves as an aggressive lymphoma with poorer outcomes than low-grade disease, though modern chemoimmunotherapy has substantially improved even high-grade outcomes. - CNS involvement confers markedly worse prognosis: one cohort reported 3-year overall mortality of 63.5% in LYG broadly versus 86.0% specifically in CNS-involved LYG, with 5-year mortality of 38–88% and median survival 14–72 months in CNS-LYG (PMC7516720). - Underlying immunodeficiency status and ability to achieve immune reconstitution (e.g., HIV control, reduction of iatrogenic immunosuppression) favorably affect outcome.

Complications: Progression to overt EBV+ diffuse large B-cell lymphoma (grade 3 transformation), organ failure from pulmonary/hepatic/renal destruction, secondary infections related to immunosuppressive therapy, hemophagocytic lymphohistiocytosis as a rare severe complication.

12. Treatment

Modern risk/grade-stratified paradigm (NCI standard of care, established by the Lancet Haematology 2023 phase 2 trial, PMID 37011643):

• Low-grade disease (grades 1–2) — immunotherapy-first, reflecting "immune-dependent" biology:

• Interferon alfa-2b — dose-escalated subcutaneous injections, starting ~7.5 million international units three times weekly, continued for up to 1 year past best response. NCIT suggestion: NCIT:C1666 (Interferon Alfa-2b); treatment_term NCIT:C15986 (Pharmacotherapy).

• High-grade disease (grade 3) — chemoimmunotherapy, reflecting "immune-independent," frankly malignant biology:

• DA-EPOCH-R (dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab) — six cycles every 3 weeks intravenously. NCIT suggestion: regimen conceptually analogous to standard aggressive B-cell lymphoma chemoimmunotherapy; therapeutic_agent components include rituximab (CHEBI/NCIT:C2185 or similar anti-CD20 monoclonal antibody term), doxorubicin, cyclophosphamide, vincristine, etoposide, prednisone.

• Rituximab monotherapy — reported in isolated case reports (e.g., mediastinal LYG achieving complete remission after 3 months of rituximab monotherapy, PMID 15693798), but with variable/unpredictable results as monotherapy; not established as standard for high-grade disease alone.

Immune reconstitution as therapy: In cases secondary to reversible immunosuppression (e.g., newly diagnosed HIV, TNF-α inhibitor use, post-transplant), reducing/discontinuing the offending immunosuppression or initiating antiretroviral therapy has produced remission of low-grade pulmonary LYG, underscoring the immune-dependent mechanism at low grade (PMC11829542).

Emerging/experimental therapies: - PD-1 checkpoint inhibition — a case report describes successful treatment of pulmonary LYG with a PD-1 inhibitor-based regimen, suggesting a role for immune checkpoint blockade as an emerging strategy, though this is not yet standard of care and mechanistic rationale (tumor PD-L1 engagement suppressing anti-EBV T-cell responses) is inferred by analogy to other EBV+ lymphomas rather than LYG-specific mechanistic data. - Hematopoietic stem cell transplantation — curative for LYG arising in the context of an underlying correctable primary immunodeficiency (e.g., DOCK8 deficiency), where HSCT resolved both the immunodeficiency and the LYG.

Supportive care: Management of pulmonary complications (may require ventilatory support in severe disease), CNS-directed therapy (high-dose methotrexate plus rituximab reported effective for higher-grade CNS-LYG), and standard supportive oncologic care.

Treatment algorithm summary: The defining modern conceptual advance is that LYG is not treated as a single entity but is bifurcated by grade into a proposed "immune-dependent" (low-grade, treat the immune deficit) versus "immune-independent" (high-grade, treat as lymphoma) disease model — directly informing the two-arm design of the pivotal 2023 trial.

13. Prevention

Given LYG's basis in EBV plus acquired/host immune dysfunction, prevention is indirect rather than primary (no LYG-specific vaccine or prophylactic agent exists):

• Primary prevention: No EBV vaccine is currently licensed for general use (EBV vaccine candidates remain in clinical trials for EBV-associated diseases broadly, not LYG-specific); minimizing unnecessary or prolonged immunosuppression, and judicious use of TNF-α inhibitors and other immunomodulatory agents with awareness of EBV-driven lymphoproliferative risk, represents a practical primary-prevention-adjacent strategy in susceptible patients.
• Secondary prevention/early detection: Surveillance for EBV-driven lymphoproliferative disease (including LYG) in patients with known primary immunodeficiency syndromes (DOCK8 deficiency, Wiskott-Aldrich syndrome, XLP, CVID), solid organ transplant recipients, and HIV-positive patients with poor immune control — enabling earlier diagnosis and grade-stratified treatment before high-grade transformation.
• Tertiary prevention: Early initiation of interferon alfa-2b in low-grade disease is explicitly framed (per the 2023 NCI trial) as reducing the risk of progression to high-grade, immune-independent disease — i.e., tertiary prevention of transformation.
• Genetic counseling: Relevant when LYG arises in the context of an underlying heritable immunodeficiency syndrome (e.g., DOCK8 deficiency, Wiskott-Aldrich syndrome), where standard genetic counseling for the primary condition applies, including consideration of carrier testing and reproductive counseling for at-risk relatives.
• Public health/prophylaxis: No specific public health intervention targets LYG; general EBV exposure is nearly universal and not itself modifiable at the population level.

14. Other Species / Natural Disease

No naturally occurring veterinary counterpart of lymphomatoid granulomatosis specifically was identified in this search (unlike, e.g., some EBV-associated human lymphomas that have partial analogs in Old World primate lymphocryptovirus infections). EBV itself is a human-tropic gammaherpesvirus (NCBITaxon:10376) without natural non-human hosts, though related lymphocryptoviruses infect other primates and can produce analogous lymphoproliferative disease in those species (relevant to comparative biology of gammaherpesvirus-driven lymphoproliferation broadly, though not documented as "lymphomatoid granulomatosis" by name in veterinary literature). No OMIA (Online Mendelian Inheritance in Animals) entry or zoonotic transmission pathway is applicable, since EBV is not zoonotic.

15. Model Organisms

No LYG-specific animal or in vitro model was identified in the literature searched. However, the broader mechanistic paradigm — EBV infection with defective T-cell immunosurveillance driving B-cell lymphoproliferation — is modeled by:

• Humanized mouse models of EBV infection (e.g., NOD/Shi-scid IL2rγnull [NOG], NOD/LtSz-scid Il2rg−/− [NSG], BALB/c Rag2−/−Il2rg−/− strains reconstituted with human hematopoietic stem cells) — these models reproduce EBV-associated B-cell lymphoproliferative disease and hemophagocytic lymphohistiocytosis, and are used to study post-transplant lymphoproliferative disease (PTLD), a mechanistically related EBV+ B-cell lymphoproliferation arising under iatrogenic immunosuppression (PMC4235711, "Humanized Mouse Models of Epstein-Barr Virus Infection and Associated Diseases").
• Immunosuppression-augmented humanized mouse models — e.g., FK506 (tacrolimus) treatment of humanized mice increases the frequency of EBV-associated lymphoproliferative disease, directly modeling the iatrogenic-immunosuppression risk pathway relevant to LYG in transplant recipients (PMC7162544).
• Checkpoint blockade studies in humanized mice — PD-1/CTLA-4 blockade has been shown to inhibit EBV-induced lymphoma growth in a cord-blood humanized mouse model, providing translational rationale (by analogy, not direct LYG data) for the emerging PD-1 inhibitor case report noted above (PMC4871349).

Model limitations relevant to LYG specifically: Existing humanized-mouse EBV-lymphoproliferation models capture generic EBV+ B-cell lymphoproliferative disease and PTLD-like biology but do not recapitulate the LYG-defining angiocentric/angioinvasive tissue tropism, multi-organ pattern (lung/skin/CNS predominance), or the specific CD4-predominant reactive T-cell microenvironment — representing a clear gap between available model systems and the human disease phenotype that would need explicit flagging (e.g., a HUMAN_MODEL_MISMATCH framing) in any KB curation.

Summary of Suggested Ontology Bindings for KB Curation

Sources

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• Humanized Mouse Models of Epstein-Barr Virus Infection and Associated Diseases. PMC4235711
• Immunosuppressive FK506 treatment leads to more frequent EBV-associated lymphoproliferative disease in humanized mice. PMC7162544
• PD-1/CTLA-4 Blockade Inhibits EBV-Induced Lymphoma Growth in a Cord Blood Humanized-Mouse Model. PMC4871349
• Case Report: Successful treatment of pulmonary lymphomatoid granulomatosis with a PD-1 inhibitor-based regimen. PMC12827129

Reference Validation

Checked with linkml-reference-validator 0.2.1.

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

• UBERON:0000955 (2 mentions) - the report calls it "CNS involvement"; UBERON calls it brain
• NCIT:C1666 (2 mentions) - the report calls it "Interferon Alfa-2b"; NCIT calls it Tyrphostin A30

Unresolved terms

These identifiers do not exist in an ontology that resolved other terms from the same prefix, so they were most likely invented:

• HP:0002316 (1 mention) - HP does not contain this term

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

• HP:0001392 (1 mention) - the report calls it "Abnormal liver morphology"; HP calls it Abnormality of the liver, and lists "Abnormal liver" among its other names
• GO:0032102 (1 mention) - the report calls it "negative regulation of response to wounding"; GO calls it negative regulation of response to external stimulus
• CL:0000624 (3 mentions) - the report calls it "CD4-positive, alpha-beta T cell", "CD4+ alpha-beta T cell"; CL calls it CD4-positive, alpha-beta T cell
• UBERON:0002048 (2 mentions) - the report calls it "lung", "Lung involvement"; UBERON calls it lung
• UBERON:0002097 (2 mentions) - the report calls it "Skin involvement"; UBERON calls it skin of body, and lists "entire integument" among its other names

Terms named inconsistently

The report gives these identifiers more than one name of its own:

• CL:0000624 - called "CD4-positive, alpha-beta T cell", "CD4+ alpha-beta T cell"
• UBERON:0002048 - called "lung", "Lung involvement"

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: ORPHA.