Disease | Demographic features | Clinical key features | Autoantibodies and possible additional features | |
Dermatomyositis | All ages. Peak incidence ages 40–60 years and 5–14 years. Female predominance. | Symmetrical weakness. Proximal > distal weakness. Neck flexor > neck extensor weakness. Dysphagia. Subacute onset. Classic dermatomyositis rash. | MDA5 |
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NXP2 |
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Mi2 |
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TIF1-γ |
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SAE1 |
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Antisynthetase and related syndromes | Adolescents/Adults. | Symmetric weakness. Proximal > distal weakness. Neck flexor > neck extensor weakness. Dysphagia. Antisynthetase syndrome:
| Jo1 |
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PL7 |
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PL12 |
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OJ |
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KS |
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ZO |
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EJ |
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Tyrosyl |
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Non-specific myositis | Adolescents/Adults. | Symmetric weakness. Proximal > distal weakness. Neck flexor > neck extensor weakness. Dysphagia. Subacute onset. Association with systemic disease. | PM-Scl (75/100) |
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RNP |
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Ku |
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SSA (Ro52, Ro60) and SSB (La) |
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Immune-mediated necrotising myopathy | All ages. Female predominance. | Severe symmetric limb weakness. Axial weakness. Muscle atrophy. Dysphagia. Very high serum creatine kinase (>10× upper limit of normal). Subacute onset. | HMGCR |
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SRP |
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‘seronegative’ |
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Inclusion body myositis | >45 years. Male predominance. Co-occurrence with autoimmune disease in one-third. | (A)symmetric weakness. Selective involvement of quadriceps and deep finger flexors. Dysphagia. Facial/axial weakness. Insidious onset. | cN-1A |
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