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Dermatomyositis

Disease Pathophysiology Research Report

2025-12-18
Falcon MONDO:0016367 Model: Edison Scientific Literature 44 citations

Disease Pathophysiology Research Report

Target Disease - Disease Name: Dermatomyositis (DM) - MONDO ID: MONDO:0005377 - Category: Autoimmune

Pathophysiology description Dermatomyositis is a systemic autoimmune microangiopathy of skin, skeletal muscle, and frequently lung, characterized by complement-mediated capillary injury, a dominant type I interferon (IFN-I) transcriptional signature, and serologically defined subtypes driven by myositis-specific autoantibodies (MSAs). Histopathology demonstrates endothelial and myofiber damage with perifascicular atrophy, perivascular/perifascicular inflammatory infiltrates enriched for CD4+ T cells and plasmacytoid dendritic cells (pDCs), and membrane attack complex (MAC; C5b-9) deposition on endomysial capillaries and the sarcolemma, linking complement activation to microvascular ischemia and tissue injury (publication: Journal of Neuromuscular Diseases, Dec 2024; https://doi.org/10.3233/jnd-230168; and supportive review) (honda2024contributionofcomplement pages 1-3, honda2024contributionofcomplement pages 8-10, cristofori2025dermatomyositisanarrative pages 2-3).

A pervasive IFN-I signature marked by MxA/ISG expression is observed in blood, skin, endothelium, and muscle, and correlates with disease activity; pDCs are present in inflamed tissue and are likely major local sources of IFN-I (publications: Current Rheumatology Reports, Sep 2024, https://doi.org/10.1007/s11926-024-01164-7; Children, Aug 2024, https://doi.org/10.3390/children11091046) (musai2024recentupdateson pages 1-2, kobayashi2024advancesinjuvenile pages 13-14). MSAs define phenotypes and risks: anti-TIF1-γ (TRIM33) and anti-NXP2 associate with malignancy; anti-MDA5 (IFIH1) correlates with clinically amyopathic presentations and high risk of rapidly progressive interstitial lung disease (RP-ILD); anti-Mi-2 (CHD4) is linked to classic cutaneous disease and favorable prognosis; anti-SAE often presents with florid skin disease and delayed weakness (publications and narrative reviews with URLs: Curr Rheumatol Rep 2024, https://doi.org/10.1007/s11926-024-01164-7; Cureus, Jul 2025, https://doi.org/10.7759/cureus.88601; Seminars in Immunopathology, Aug 2025, https://doi.org/10.1007/s00281-025-01054-9) (musai2024recentupdateson pages 1-2, cristofori2025dermatomyositisanarrative pages 3-4, ali2025dermatomyositisfocuson pages 1-2, cristofori2025dermatomyositisanarrative pages 2-3).

Therapeutically, the IFN–JAK/STAT axis is targetable: JAK inhibitors (tofacitinib, baricitinib, ruxolitinib; and selective TYK2/JAK1 inhibitor brepocitinib) have shown improvements in refractory cutaneous and systemic disease, including RP-ILD, with emerging safety considerations such as opportunistic infections (publication dates and URLs: Frontiers in Immunology, Mar 2024, https://doi.org/10.3389/fimmu.2024.1382728; Rheumatology International, Mar 2024, https://doi.org/10.1007/s00296-024-05551-2; Expert Opin Pharmacother, Aug 2024, https://doi.org/10.1080/14656566.2024.2392021; Clin Exp Rheumatology, Mar 2025, https://doi.org/10.55563/clinexprheumatol/eeglsa) (ma2024therapeuticefficacyand pages 1-2, harada2024baricitinibforantimelanoma pages 7-8, wallwork2024currentevidencefor pages 1-3, paik2025brepocitinibapotent pages 1-2).

1) Core Pathophysiology - Primary mechanisms: immune-mediated microangiopathy with complement MAC (C5b-9) deposition injuring endomysial capillaries and myofibers; ischemia produces perifascicular atrophy. Concurrent IFN-I–dominated innate immune activation amplifies endothelial activation, antigen presentation (MHC-I upregulation), and leukocyte recruitment (Journal of Neuromuscular Diseases, 2024; Cureus narrative review, 2025) (honda2024contributionofcomplement pages 1-3, honda2024contributionofcomplement pages 8-10, cristofori2025dermatomyositisanarrative pages 2-3). - Dysregulated molecular pathways: IFN-I signaling (IFNAR–JAK1/TYK2–STAT1/2), complement activation and MAC assembly, chemokine axes (e.g., CX3CL1–CX3CR1 in lung), and downstream cytokine networks; in anti-MDA5 DM, immune complexes may engage endosomal TLRs to further induce IFN-α (Rheumatology International, 2024; Current Rheumatology Reports, 2024) (harada2024baricitinibforantimelanoma pages 7-8, musai2024recentupdateson pages 1-2). - Affected cellular processes: endothelial activation and injury, antigen presentation/MHC-I upregulation in myofibers, pDC-driven IFN production, macrophage activation/polarization, keratinocyte apoptosis and interface dermatitis in skin (Children, 2024; Current Rheumatology Reports, 2024) (kobayashi2024advancesinjuvenile pages 13-14, musai2024recentupdateson pages 1-2).

2) Key Molecular Players - Genes/Proteins (HGNC): TRIM33/TIF1-γ, MORC3/NXP2, IFIH1/MDA5, CHD4/Mi-2, SAE1/SAE2; IFNAR1/2, JAK1, TYK2, STAT1; complement C5–C9 (C5b-9). Anti-TIF1-γ/NXP2 associate with malignancy; anti-MDA5 with RP-ILD; anti-Mi-2 with favorable course; anti-SAE with cutaneous-predominant onset (Current Rheumatology Reports, 2024; Seminars in Immunopathology, 2025; Cureus, 2025) (musai2024recentupdateson pages 1-2, ali2025dermatomyositisfocuson pages 1-2, cristofori2025dermatomyositisanarrative pages 2-3). - Chemical Entities (CHEBI): JAK inhibitors (tofacitinib, baricitinib, ruxolitinib), TYK2/JAK1 inhibitor brepocitinib; IVIG—partly effective via complement inhibition (Frontiers in Immunology, 2024; Clin Exp Rheumatology, 2025; Journal of Neuromuscular Diseases, 2024) (ma2024therapeuticefficacyand pages 1-2, paik2025brepocitinibapotent pages 1-2, honda2024contributionofcomplement pages 1-3). - Cell Types (CL): endothelial cells, pDCs, macrophages (CD163+ subsets), CD4+ and CD8+ T cells, B cells/plasma cells, keratinocytes, lung alveolar macrophages (Children, 2024; Current Rheumatology Reports, 2024; Journal of Neuromuscular Diseases, 2024) (kobayashi2024advancesinjuvenile pages 13-14, musai2024recentupdateson pages 1-2, honda2024contributionofcomplement pages 1-3). - Anatomical Locations (UBERON): skin, skeletal muscle, lung (Cureus, 2025; Current Rheumatology Reports, 2024) (cristofori2025dermatomyositisanarrative pages 2-3, musai2024recentupdateson pages 1-2).

3) Biological Processes (GO terms) - Type I interferon signaling pathway (GO:0060337): central DM signature in skin/muscle/blood (Current Rheumatology Reports, 2024) (musai2024recentupdateson pages 1-2). - Complement activation, MAC assembly (GO:0006956): endomysial capillary and sarcolemmal C5b-9 deposition (Journal of Neuromuscular Diseases, 2024) (honda2024contributionofcomplement pages 1-3). - Endothelial cell activation (GO:0042118) and leukocyte chemotaxis (GO:0030595): microangiopathy and perivascular inflammation (Journal of Neuromuscular Diseases, 2024) (honda2024contributionofcomplement pages 1-3). - Antigen processing and presentation of peptide antigen via MHC class I (GO:0002474): myofiber MHC-I overexpression (Cureus, 2025) (cristofori2025dermatomyositisanarrative pages 2-3). - Cellular response to interferon-alpha/beta (GO:0035455/GO:0035456): broad ISG upregulation correlating with activity (Clin Exp Rheumatology, 2025) (paik2025brepocitinibapotent pages 1-2). - NET formation/neutrophil activation (GO:0038061/GO:0042119) and fibrotic pathways including TGF-β signaling in ILD (GO:0007179): implicated particularly in anti-MDA5 RP-ILD (Rheumatology International, 2024) (harada2024baricitinibforantimelanoma pages 7-8).

4) Cellular Components - Endomysial capillary and perimysial vessels: sites of MAC deposition and vasculopathy (Journal of Neuromuscular Diseases, 2024) (honda2024contributionofcomplement pages 1-3). - Sarcolemma: MAC deposition and myofiber injury (Journal of Neuromuscular Diseases, 2024) (honda2024contributionofcomplement pages 1-3). - Dermoepidermal junction: immunoglobulin/complement deposition and interface dermatitis (Cureus, 2025) (cristofori2025dermatomyositisanarrative pages 2-3). - Cytosol/nucleus of myofibers and keratinocytes: intracellular autoantigens (Mi-2/CHD4, TIF1-γ/TRIM33, NXP2/MORC3, SAE1/2) (Current Rheumatology Reports, 2024) (musai2024recentupdateson pages 1-2). - Extracellular space and alveolar compartments: cytokine/chemokine milieu and macrophage activation in ILD (Rheumatology International, 2024) (harada2024baricitinibforantimelanoma pages 7-8).

5) Disease Progression (sequence of events) - Trigger(s): genetic susceptibility and environmental stimuli (e.g., viral RNA sensed by MDA5, UV) initiate innate immune activation with strong IFN-I production by pDCs and other sources (Current Rheumatology Reports, 2024) (musai2024recentupdateson pages 1-2). - Vascular phase: antibody/complement-mediated endothelial injury (MAC deposition) causes capillary dropout and ischemia; clinically, nailfold changes and painful cutaneous ulcers may appear (Journal of Neuromuscular Diseases, 2024; Cureus, 2025) (honda2024contributionofcomplement pages 1-3, cristofori2025dermatomyositisanarrative pages 3-4). - Muscle phase: hypoperfusion and IFN-driven immune activation promote perifascicular atrophy, MHC-I upregulation, and inflammatory infiltrates with macrophages, CD4+ T cells, B cells; proximal weakness ensues (Cureus, 2025) (cristofori2025dermatomyositisanarrative pages 2-3). - Lung involvement: in anti-MDA5 disease, IFN-driven chemokines (CX3CL1) recruit CX3CR1+ M2 macrophages to the lung, fueling ILD and potential fibrosis; RP-ILD may develop with high mortality without aggressive therapy (Rheumatology International, 2024) (harada2024baricitinibforantimelanoma pages 7-8).

6) Phenotypic Manifestations (HP terms) - Proximal muscle weakness (HP:0003701), elevated muscle enzymes, and dysphagia (HP:0002015) reflect myofiber injury and inflammation (Cureus, 2025) (cristofori2025dermatomyositisanarrative pages 2-3). - Heliotrope rash (HP:0001002), Gottron papules (HP:0031408), poikiloderma and photosensitivity (HP:0000992) reflect IFN-driven skin inflammation with interface dermatitis and complement deposition (Cureus, 2025; Seminars in Immunopathology, 2025) (cristofori2025dermatomyositisanarrative pages 2-3, ali2025dermatomyositisfocuson pages 1-2). - Nailfold capillary abnormalities (HP:0030831) reflect microangiopathy (Cureus, 2025) (cristofori2025dermatomyositisanarrative pages 3-4). - Interstitial lung disease (HP:0006530), especially RP-ILD in anti-MDA5 DM, reflects IFN/macrophage-driven lung injury and fibrosis (Rheumatology International, 2024) (harada2024baricitinibforantimelanoma pages 7-8). - Calcinosis cutis (HP:0000987), especially in juvenile/anti-NXP2 disease, indicates chronic tissue damage and dystrophic calcification (Current Rheumatology Reports, 2024) (musai2024recentupdateson pages 1-2).

Evidence items (primary data and statistics; URLs and dates) - Complement microangiopathy and perifascicular atrophy: “deposition of the membrane attack complex (C5b-9) in endomysial capillaries” associates with endothelial/myofiber injury and ischemia; juvenile DM shows capillary loss and small-vessel angiopathy (Journal of Neuromuscular Diseases, Dec 2024; https://doi.org/10.3233/jnd-230168) (honda2024contributionofcomplement pages 1-3, honda2024contributionofcomplement pages 8-10). - IFN score and prognosis in anti-MDA5 DM: A 2023 cohort showed high IFN-I score correlates with disease activity and poor 3‑month survival; patients with IFN‑I score >4.9 had lower 3‑month survival (72.9% vs. 100%; P=0.044) (Frontiers in Immunology, Mar 2023; https://doi.org/10.3389/fimmu.2023.1151695) (rocca2023targetingintracellularpathways pages 3-4). - JAK inhibitors in DM/PM (single‑arm meta-analysis, 7 studies, n=91): mean CDASI improvement −17.67 (95% CI −20.94 to −14.41); MMT +10.31 (95% CI −2.83 to 23.46). Subgroup CDASI reductions: ruxolitinib −20.00, tofacitinib −18.29, baricitinib −11.2. Reported safety included orolabial HSV and two thromboembolic events (Frontiers in Immunology, Mar 2024; https://doi.org/10.3389/fimmu.2024.1382728) (ma2024therapeuticefficacyand pages 1-2). - Anti-MDA5 DM-ILD treated with JAK inhibitors (literature review/case series): pooled survival ~75.9% (predominantly tofacitinib); baricitinib case series (n=3) improved lung opacities and rescued 2/3; notable CMV reactivation risk—close monitoring recommended (Rheumatology International, Mar 2024; https://doi.org/10.1007/s00296-024-05551-2) (harada2024baricitinibforantimelanoma pages 7-8). - JDM JAK inhibitor overview (systematic narrative): Across compiled reports to 2023, muscle improvement in 51/53 (96%); skin improvement in 109/152 (72%); frequent steroid reduction; infections included EBV/CMV/HSV and bacterial/fungal events; hematologic/lipid changes reported (Expert Rev Clin Immunol, Feb 2024; https://doi.org/10.1080/1744666x.2024.2312819) (kim2024updatesonefficacy pages 3-4, kim2024updatesonefficacy pages 13-14). - Rationale for TYK2/JAK1 inhibition: IFN-I signaling via IFNAR engages JAK1/TYK2; selective TYK2/JAK1 blockade (brepocitinib) reduces IFN-α/β, IL-12/23, IFN-γ pathways; large phase 3 trial in DM ongoing (VALOR, NCT0543726) (Clin Exp Rheumatology, Mar 2025; https://doi.org/10.55563/clinexprheumatol/eeglsa) (paik2025brepocitinibapotent pages 1-2).

Expert opinions and analysis - Consensus in recent expert reviews is that DM is best conceptualized as an IFN-driven microangiopathy with autoantibody-defined endotypes that dictate organ risk (malignancy vs. RP-ILD) and may benefit from mechanism-guided therapy, particularly IFN–JAK/STAT pathway inhibition; however, infectious risks (e.g., CMV) and heterogeneity of responses necessitate risk-stratified, monitored use (Current Rheumatology Reports, 2024; Expert Opin Pharmacother, 2024; Rheumatology International, 2024) (musai2024recentupdateson pages 1-2, wallwork2024currentevidencefor pages 1-3, harada2024baricitinibforantimelanoma pages 7-8).

Current applications and real-world implementations - Off-label JAK inhibitor use for refractory cutaneous DM and anti-MDA5 DM-ILD (tofacitinib, baricitinib, ruxolitinib) with documented improvements in CDASI, muscle scores, and ILD survival in observational cohorts; viral surveillance and infection prophylaxis protocols increasingly implemented in high-risk subsets (Frontiers in Immunology, 2024; Rheumatology International, 2024) (ma2024therapeuticefficacyand pages 1-2, harada2024baricitinibforantimelanoma pages 7-8). - IVIG employed to modulate humoral/complement pathways, with mechanistic support that it can block endomysial complement deposition (Journal of Neuromuscular Diseases, 2024) (honda2024contributionofcomplement pages 8-10). - Serology-driven risk management: anti-TIF1-γ/NXP2 prompting intensified cancer screening; anti-MDA5 prompting early, aggressive lung-directed therapy and IFN-pathway targeting (Current Rheumatology Reports, 2024; Cureus, 2025) (musai2024recentupdateson pages 1-2, cristofori2025dermatomyositisanarrative pages 3-4).

Ontology-annotated annotations (HGNC, GO, CL, UBERON, CHEBI, HP) - Genes/Proteins (HGNC): TRIM33 (TIF1-γ), MORC3 (NXP2), IFIH1 (MDA5), CHD4 (Mi-2), SAE1/SAE2; IFNAR1/2, JAK1, TYK2, STAT1; C5–C9 (MAC) (musai2024recentupdateson pages 1-2, honda2024contributionofcomplement pages 1-3). - GO Biological processes: type I interferon signaling (GO:0060337); complement activation (GO:0006956); endothelial activation (GO:0042118); leukocyte chemotaxis (GO:0030595); antigen presentation via MHC-I (GO:0002474); pulmonary fibrosis/TGF-β signaling (GO:0007179) (honda2024contributionofcomplement pages 1-3, musai2024recentupdateson pages 1-2, harada2024baricitinibforantimelanoma pages 7-8). - Cellular components: endomysial capillary, perimysial vessel, sarcolemma, dermoepidermal junction, cytosol/nucleus, extracellular space (honda2024contributionofcomplement pages 1-3, cristofori2025dermatomyositisanarrative pages 2-3). - Cell types (CL): pDCs (CL:0000911), macrophages (CL:0000235), endothelial cells (CL:0000115), CD4+ and CD8+ T cells, B cells/plasma cells, keratinocytes, alveolar macrophages (kobayashi2024advancesinjuvenile pages 13-14, musai2024recentupdateson pages 1-2, honda2024contributionofcomplement pages 1-3). - Anatomical locations (UBERON): skin (UBERON:0002097), skeletal muscle (UBERON:0002090), lung (UBERON:0002048) (cristofori2025dermatomyositisanarrative pages 2-3, musai2024recentupdateson pages 1-2). - Chemical entities (CHEBI): tofacitinib, baricitinib, ruxolitinib, brepocitinib, intravenous immunoglobulin (ma2024therapeuticefficacyand pages 1-2, paik2025brepocitinibapotent pages 1-2, honda2024contributionofcomplement pages 1-3). - Phenotypes (HP): proximal muscle weakness (HP:0003701), heliotrope rash (HP:0001002), Gottron papules (HP:0031408), photosensitivity (HP:0000992), dysphagia (HP:0002015), interstitial lung disease (HP:0006530), calcinosis cutis (HP:0000987), nailfold capillary abnormalities (HP:0030831) (ali2025dermatomyositisfocuson pages 1-2, cristofori2025dermatomyositisanarrative pages 2-3, harada2024baricitinibforantimelanoma pages 7-8).

Direct quotes (selected) - “deposition of the membrane attack complex (C5b-9) in endomysial capillaries” (Journal of Neuromuscular Diseases, 2024; https://doi.org/10.3233/jnd-230168) (honda2024contributionofcomplement pages 1-3). - “type I interferon gene transcription scores in blood correlate strongly with DM disease activity” and “decrease significantly with immunomodulatory therapy” (Clin Exp Rheumatology, 2025; https://doi.org/10.55563/clinexprheumatol/eeglsa) (paik2025brepocitinibapotent pages 1-2). - In anti-MDA5 DM-ILD treated with JAK inhibitors, “the survival rate was 75.9%” in pooled literature, and “the incidence of CMV reactivation appeared to be high” (Rheumatology International, 2024; https://doi.org/10.1007/s00296-024-05551-2) (harada2024baricitinibforantimelanoma pages 7-8).

Recent developments (2023–2024 priority) - IFN-I score as prognostic biomarker in anti-MDA5 DM: high baseline IFN-I score associated with higher disease activity and lower 3‑month survival (72.9% vs 100%) (Frontiers in Immunology, Mar 2023; https://doi.org/10.3389/fimmu.2023.1151695) (rocca2023targetingintracellularpathways pages 3-4). - JAK inhibitors meta-analysis (Mar 2024) demonstrates clinically meaningful cutaneous improvement (CDASI −17.67) and muscle strength gains; safety acceptable but vigilance for thromboembolism and infection required (Frontiers in Immunology, Mar 2024; https://doi.org/10.3389/fimmu.2024.1382728) (ma2024therapeuticefficacyand pages 1-2). - Anti-MDA5 DM-ILD case series/review (Mar 2024) supports JAK inhibition in RP-ILD with survival ~75.9% and highlights CMV risk and need for monitoring (Rheumatology International, Mar 2024; https://doi.org/10.1007/s00296-024-05551-2) (harada2024baricitinibforantimelanoma pages 7-8). - Expert therapeutic overviews (Aug 2024) outline growing evidence base and active randomized trials of JAK/TYK2 inhibitors in adult and juvenile DM (Expert Opin Pharmacother, Aug 2024; https://doi.org/10.1080/14656566.2024.2392021) (wallwork2024currentevidencefor pages 1-3).

Applications, implementations, and safety - Implementation: off-label JAK inhibitor regimens (e.g., tofacitinib 5–10 mg BID; baricitinib 2–4 mg daily) with multi-drug background therapy, serial IFN score and viral surveillance (CMV/EBV/BK) in high-risk anti-MDA5 subsets; IVIG used to curb complement-mediated injury (Frontiers in Immunology, 2024; Journal of Neuromuscular Diseases, 2024) (ma2024therapeuticefficacyand pages 1-2, honda2024contributionofcomplement pages 8-10). - Safety: infections (HSV, CMV, bacterial/fungal), cytopenias, lipids/weight changes; in anti-MDA5 DM-ILD, CMV reactivation is common enough to warrant pre-emptive monitoring/antivirals and temporary drug holds (Expert Rev Clin Immunol, 2024; Rheumatology International, 2024) (kim2024updatesonefficacy pages 13-14, harada2024baricitinibforantimelanoma pages 7-8).

Structured artifacts (ontology-mapped summary) | Category | Entity (preferred name) | Ontology tag | Mechanistic role in DM | Phenotype/clinical association | Key evidence | Notes | |---|---|---|---|---|---|---| | Pathway | Type I interferon pathway (IFNA/IFNB → IFNAR1/2 → JAK1/TYK2 → STAT1) | IFNA/IFNB, IFNAR1, IFNAR2, JAK1, TYK2, STAT1 (HGNC); GO:0060337 (type I interferon signaling) | Drives a dominant transcriptional signature (ISGs) in skin and muscle; promotes MHC-I upregulation and immune cell recruitment | Correlates with disease activity, anti‑MDA5 severity, and poor prognosis in RP‑ILD | (musai2024recentupdateson pages 1-2, kim2025juveniledermatomyositisupdates pages 1-2, cristofori2025dermatomyositisanarrative pages 2-3) | Therapeutic target of JAK inhibitors; measurable IFN score biomarker | | Complement | Complement membrane attack complex (C5b-9 / MAC) | C5 (HGNC); GO:0006956 (complement activation) ; Cellular component: extracellular space / endomysial capillary | Deposition on endomysial capillaries and sarcolemma causing endothelial/myofiber injury and microangiopathy | Associated with perifascicular atrophy, capillary loss, and juvenile DM vascular pathology | (honda2024contributionofcomplement pages 1-3, honda2024contributionofcomplement pages 8-10, cristofori2025dermatomyositisanarrative pages 3-4) | IVIG can block complement deposition; complement implicated in antibody-mediated endothelial damage | | Cell type | Plasmacytoid dendritic cell (pDC) | CL:0000911 (pDC) ; GO:0034340 (type I interferon production) | Main source of type I IFNs in affected tissues; present in inflamed muscle and skin, amplifies IFN signature | Contributes to local inflammation and IFN-driven tissue damage | (kobayashi2024advancesinjuvenile pages 13-14, musai2024recentupdateson pages 1-2, honda2024contributionofcomplement pages 1-3) | pDCs link innate viral-sensing to autoimmunity in DM | | Cell type | Endothelial cell | CL:0000115 (endothelial cell); GO:0042118 (endothelial cell activation) ; Cellular component: endomysial capillary | Target of autoantibody- and complement-mediated injury leading to microangiopathy and ischemia | Perivascular inflammation, capillary dropout, microhemorrhages; drives perifascicular changes | (honda2024contributionofcomplement pages 1-3, honda2024contributionofcomplement pages 8-10) | Endothelial activation biomarkers associate with disease activity | | Tissue/cell | Skeletal muscle fiber (myofiber) | UBERON:0002090 (skeletal muscle) ; Cellular component: sarcolemma, cytosol, nucleus | Display MHC‑I upregulation, atrophy/necrosis from hypoperfusion and immune attack; regenerative changes | Proximal symmetric weakness, elevated CK, perifascicular atrophy on biopsy | (cristofori2025dermatomyositisanarrative pages 2-3, musai2024recentupdateson pages 1-2) | Autoantibody entry into myofibers may disrupt intracellular targets | | Cell type | Macrophage (incl. CD163+ subsets) | CD163 (HGNC); CL:0000235 (macrophage) | Produce cytokines, present antigen, participate in interferon-driven inflammation and tissue remodeling | Associated with perimysial/perifascicular infiltration; implicated in anti‑MDA5 lung pathology | (musai2024recentupdateson pages 1-2, honda2024contributionofcomplement pages 8-10) | Macrophage polarization (M1/M2) influences damage vs repair | | Cell type | T cell (CD4+, CD8+) | CD4, CD8A (HGNC); CL terms for T cell subsets | CD4+ perivascular infiltrates; CD8+ implicated in cytotoxic responses and paraneoplastic links | Lymphocytic infiltration on muscle biopsy; CD8+ associated with some cancer‑linked phenotypes | (cristofori2025dermatomyositisanarrative pages 2-3, musai2024recentupdateson pages 1-2) | T cell roles vary by autoantibody-defined subtype | | Cell type | B cell / plasma cell | CD19, CD20 (HGNC); CL:0000236 (B cell) | Source of myositis-specific autoantibodies; antigen presentation and local antibody production | Autoantibodies stratify phenotypes (malignancy risk, ILD risk) and guide therapy (rituximab) | (musai2024recentupdateson pages 1-2, kim2025juveniledermatomyositisupdates pages 1-2) | B‑cell depletion and emerging CD19 CAR‑T approaches under investigation | | Cell type | Keratinocyte | CL:0000134 (epidermal keratinocyte) ; Cellular component: dermoepidermal junction | Responds to IFN signaling and shows immune complex / complement deposition → apoptosis and rash | Gottron papules, heliotrope rash, poikiloderma; cutaneous ulceration in severe/anti‑MDA5 cases | (cristofori2025dermatomyositisanarrative pages 2-3, ali2025dermatomyositisfocuson pages 1-2) | Skin changes mirror muscle IFN-driven pathology | | Cell type | Lung alveolar macrophage | CL:0000235 (macrophage); UBERON lung alveolus | Participate in IFN/cytokine networks and macrophage activation contributing to ILD | Central in anti‑MDA5 RP‑ILD pathogenesis and respiratory failure | (kim2025juveniledermatomyositisupdates pages 1-2, musai2024recentupdateson pages 1-2) | Therapies targeting IFN/JAK may modulate pulmonary macrophage activation | | Autoantigen / autoantibody | TRIM33 / TIF1-γ | TRIM33 (HGNC) / anti‑TIF1-γ MSA | Autoantigen targeted by autoantibodies; potential paraneoplastic antigen linking tumor neoantigens to autoimmunity | Strongly associated with cancer‑associated DM and specific cutaneous phenotypes | (cristofori2025dermatomyositisanarrative pages 2-3, musai2024recentupdateson pages 1-2) | TIF1-γ serology used for cancer risk stratification | | Autoantigen / autoantibody | NXP2 | NXP2 (MORC3?) — NXP2 (gene) (HGNC) | Nuclear matrix protein targeted by autoantibodies; associated with distinct muscle/skin pathology | Linked to adult cancer risk, calcinosis, severe weakness and dysphagia | (cristofori2025dermatomyositisanarrative pages 2-3, musai2024recentupdateson pages 1-2) | Phenotype associations vary by age group | | Autoantigen / autoantibody | MDA5 / IFIH1 | IFIH1 (HGNC) / anti‑MDA5 MSA | Viral RNA sensor; autoantibodies linked to IFN overactivation and macrophage/monocyte dynamics | Clinically amyopathic DM, high risk of rapidly progressive ILD (RP‑ILD) and poor pulmonary prognosis | (kim2025juveniledermatomyositisupdates pages 1-2, musai2024recentupdateson pages 1-2) | Geographic/seasonal patterns noted; anti‑MDA5 titer correlates with severity | | Autoantigen / autoantibody | Mi‑2 / CHD4 | CHD4 (HGNC) / anti‑Mi‑2 MSA | Autoantibody associated with classic DM histology; less oncologic risk | Favorable prognosis, characteristic cutaneous findings | (musai2024recentupdateson pages 1-2, ali2025dermatomyositisfocuson pages 1-2) | Mi‑2 subtype historically linked to good treatment response | | Autoantigen / autoantibody | SAE1 / SAE2 | SAE1, SAE2 (HGNC) / anti‑SAE MSA | Autoantibody linked to cutaneous‑predominant onset and systemic features | Florid skin disease, delayed muscle weakness, possible increased cancer risk | (ali2025dermatomyositisfocuson pages 1-2, musai2024recentupdateson pages 1-2) | SAE serology marks a distinct clinical trajectory | | Organ site | Skin | UBERON:0002097 (skin) ; Cellular component: dermoepidermal junction | Primary target of IFN-driven inflammation, immune complex/complement deposition | Pathognomonic rashes (Gottron, heliotrope), ulcers, photosensitivity; reflects systemic disease activity | (cristofori2025dermatomyositisanarrative pages 2-3, ali2025dermatomyositisfocuson pages 1-2) | Skin biopsies and capillaroscopy provide diagnostic/prognostic clues | | Organ site | Skeletal muscle | UBERON:0002090 (skeletal muscle) ; Cellular component: endomysial capillary, sarcolemma | Site of microangiopathy, myofiber ischemia/necrosis, MHC‑I upregulation and immune infiltration | Proximal muscle weakness, elevated muscle enzymes, biopsy changes including perifascicular atrophy | (honda2024contributionofcomplement pages 1-3, musai2024recentupdateson pages 1-2) | Muscle MRI and biopsy remain key diagnostic tools | | Organ site | Lung | UBERON:0002048 (lung) ; GO:0035966 (pulmonary fibrosis) | Target of inflammatory and fibrotic sequelae driven by IFN/cytokines and macrophage activation | Interstitial lung disease (ILD), rapidly progressive ILD in anti‑MDA5 patients | (kim2025juveniledermatomyositisupdates pages 1-2, musai2024recentupdateson pages 1-2) | ILD is a major determinant of mortality in specific DM subtypes | | Therapeutic | Tofacitinib (JAK1/2/3 inhibitor) | CHEBI:tofacitinib (drug) ; acts on JAK/STAT pathway | Inhibits downstream signaling of type I IFN and other cytokines to reduce inflammation | Improves cutaneous disease and some muscle outcomes in refractory DM (case series/meta-analyses) | (musai2024recentupdateson pages 1-2, kim2025juveniledermatomyositisupdates pages 1-2, ali2025dermatomyositisfocuson pages 1-2) | Off‑label use reported; safety profile includes infection risk | | Therapeutic | Baricitinib (JAK1/2 inhibitor) | CHEBI:baricitinib | JAK inhibition reducing IFN signaling; reported benefit in anti‑MDA5 ILD case series | Case series report lung improvement and survival benefit in some cohorts | (kim2025juveniledermatomyositisupdates pages 1-2, musai2024recentupdateson pages 1-2, honda2024contributionofcomplement pages 8-10) | Monitoring for opportunistic infections and CMV reactivation advised | | Therapeutic | Ruxolitinib (JAK1/2 inhibitor) | CHEBI:ruxolitinib | JAK inhibition, targets IFN and other cytokine signaling | Case reports/series show cutaneous and systemic benefit | (musai2024recentupdateson pages 1-2, ali2025dermatomyositisfocuson pages 1-2) | Topical and systemic formulations have been used in refractory cases | | Therapeutic | Brepocitinib (TYK2/JAK1 inhibitor) | CHEBI:brepocitinib | Inhibits TYK2/JAK1 to reduce IFN‑α/β and other cytokine signaling; under phase 3 study in DM | Rationale for use based on IFN biology; large trials ongoing (VALOR) | (honda2024contributionofcomplement pages 8-10, musai2024recentupdateson pages 1-2) | Potential to target multiple pathogenic cytokines with oral therapy | | Therapeutic | Intravenous immunoglobulin (IVIG) | CHEBI:immunoglobulin (IVIG) | Modulates Fc receptors, neutralizes autoantibodies, and can inhibit complement deposition | Effective in refractory cutaneous and muscle disease; may reduce complement-mediated injury | (honda2024contributionofcomplement pages 1-3, honda2024contributionofcomplement pages 8-10) | Mechanisms include complement inhibition and immune modulation |

Table: Concise knowledge‑base table mapping key entities (pathways, cells, autoantigens, organs, therapies) to ontology tags, mechanistic roles, clinical associations, and supporting evidence (context IDs). Useful for structured disease annotation and rapid reference.

Evidence catalog (with PMIDs/DOIs provided via URLs where available) - Complement, microangiopathy, perifascicular atrophy and IFN biomarkers in DM: Journal of Neuromuscular Diseases, Dec 2024; https://doi.org/10.3233/jnd-230168 (honda2024contributionofcomplement pages 1-3, honda2024contributionofcomplement pages 8-10). - IFN-driven pathogenesis and autoantibody-defined endotypes: Current Rheumatology Reports, Sep 2024; https://doi.org/10.1007/s11926-024-01164-7 (musai2024recentupdateson pages 1-2). - pDCs and IFN signature in pediatric disease; vasculopathy: Children, Aug 2024; https://doi.org/10.3390/children11091046 (kobayashi2024advancesinjuvenile pages 13-14). - Anti-MDA5 DM-ILD pathogenesis and JAK inhibition outcomes and risks: Rheumatology International, Mar 2024; https://doi.org/10.1007/s00296-024-05551-2 (harada2024baricitinibforantimelanoma pages 7-8). - JAK inhibitor meta-analysis (DM/PM): Frontiers in Immunology, Mar 2024; https://doi.org/10.3389/fimmu.2024.1382728 (ma2024therapeuticefficacyand pages 1-2). - JDM JAK inhibitor outcomes and safety: Expert Rev Clin Immunol, Feb 2024; https://doi.org/10.1080/1744666x.2024.2312819 (kim2024updatesonefficacy pages 3-4, kim2024updatesonefficacy pages 13-14). - TYK2/JAK1 rationale (brepocitinib) and IFN score–activity correlations: Clin Exp Rheumatology, Mar 2025; https://doi.org/10.55563/clinexprheumatol/eeglsa (paik2025brepocitinibapotent pages 1-2). - Integrative clinical narrative for DM skin-muscle-malignancy linkages: Cureus, Jul 2025; https://doi.org/10.7759/cureus.88601 (cristofori2025dermatomyositisanarrative pages 2-3, cristofori2025dermatomyositisanarrative pages 3-4).

Limitations and open questions - Most interventional evidence remains observational; high-quality randomized, controlled trials of JAK/TYK2 inhibitors and other targeted agents are ongoing. Infection risks, optimal dosing, biomarkers for selection/monitoring (e.g., IFN score cutoffs), and long-term malignancy outcomes by MSA subtype remain active areas of research (Expert Opin Pharmacother, 2024; Clin Exp Rheumatology, 2025) (wallwork2024currentevidencefor pages 1-3, paik2025brepocitinibapotent pages 1-2).

References

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  2. (honda2024contributionofcomplement pages 8-10): Masaya Honda, Fumitaka Shimizu, Ryota Sato, and Masayuki Nakamori. Contribution of complement, microangiopathy and inflammation in idiopathic inflammatory myopathies. Journal of Neuromuscular Diseases, 11:5-16, Dec 2024. URL: https://doi.org/10.3233/jnd-230168, doi:10.3233/jnd-230168. This article has 6 citations and is from a peer-reviewed journal.

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