Clinical Features, Frequencies & Key Associations
| MAJOR DERMATOMYOSITIS AUTOANTIBODIES | |||||
| Antibody | Target/Function | Key Clinical Features | Adult DM Frequency | Juvenile DM Frequency | Special Associations |
|---|---|---|---|---|---|
| Anti-Synthetases (Anti-Jo-1, Anti-PL-7) |
Intracytoplasmic protein synthesis |
Anti-synthetase syndrome: • Myositis + "mechanic's hands" • Erosive polyarthritis • Fever + Raynaud phenomenon • 70% develop ILD (anti-Jo-1) • May have negative ANA (cytoplasmic target) |
Up to 20% | 1-3% | High ILD Risk Most predictive for pulmonary disease |
| Anti-TIF1-γ (p155) |
Cell proliferation, apoptosis, innate immunity |
Strongly associated with malignancy • Extensive cutaneous disease • Palmar hyperkeratotic papules • Psoriasiform lesions • Red-on-white telangiectatic patches • Ovoid palatal patch |
20-40% | ~25% | MALIGNANCY Most strongly associated |
| Anti-NXP-2 (p140) |
Nuclear transcription, RNA metabolism |
• Malignancy risk (especially men) • Calcinosis (adults & juveniles) • Prominent muscle involvement • Myalgias, peripheral edema • Dysphagia • Relatively mild skin disease |
10-20% | ~25% | MALIGNANCY + Calcinosis |
| Anti-MDA5 (CADM-140) |
Innate immunity (IFIH1/MDA5) |
Dermato-pulmonary syndrome • Rapidly progressive ILD • Often clinically amyopathic DM • Periungual ulcerations • Gottron papule ulcerations • Tender palmar macules/papules • Oral ulcers + prominent alopecia • Arthritis |
5-20% | N/A | Rapidly Progressive ILD Often fatal, esp. East Asian |
| Anti-Mi-2 | Helicase - transcription |
• Classic DM with hallmark cutaneous disease • Milder muscle disease • Good response to treatment • Higher rates near equator (UV link) |
15% | <10% | Good Prognosis UV radiation link |
| Anti-SAE | Post-translational modification |
• Adult DM • May initially present as clinically amyopathic DM |
5% | N/A | Amyopathic presentation |
| Anti-SRP | Protein translocation |
Acute-onset necrotizing myopathy • Severe weakness • High creatine kinase (CK) • May be refractory to treatment |
5% | <1% | Treatment Refractory Severe myopathy |
| MALIGNANCY ASSOCIATIONS | ||
| Risk Factors | Key Statistics | Clinical Action |
|---|---|---|
|
• Anti-TIF1-γ (strongest) • Anti-NXP-2 (esp. men) • Older age • Male sex • Dysphagia • Cutaneous ulcers |
• 80% of cancer-associated DM have anti-TIF1-γ OR anti-NXP-2 • Anti-TIF1-γ most strongly predictive • Higher risk in men with anti-NXP-2 |
Comprehensive malignancy screening in adults with these antibodies |
| INTERSTITIAL LUNG DISEASE (ILD) ASSOCIATIONS | ||
| High-Risk Antibodies | Clinical Pattern | Prognosis |
|---|---|---|
|
Anti-Jo-1: • 70% develop ILD • Most predictive |
Anti-synthetase syndrome with chronic progressive ILD | Major cause of morbidity/mortality |
|
Anti-MDA5: • Rapidly progressive • Even in amyopathic DM |
Dermato-pulmonary syndrome, often fatal ILD | Often fatal, especially East Asian populations |
| DIAGNOSTIC & PROGNOSTIC PEARLS | |
| Diagnostic Considerations | Prognostic Indicators |
|---|---|
|
• Negative ANA possible: Anti-synthetase antibodies target cytoplasmic antigens • Comprehensive myositis panel recommended for subtype definition • Humoral immune process: Complement activation → capillary damage |
• Best prognosis: Anti-Mi-2 (good treatment response) • Worst prognosis: Anti-SRP (treatment refractory), Anti-MDA5 (rapidly progressive ILD) • Calcinosis: More common with anti-NXP-2 |