Comparative features in selected immune myopathy syndromes
| Myopathy syndrome | Clinical features | Pathological features |
|---|---|---|
| SRP antibodies | Onset: autumn, acute, adultWeakness: severe, proximalSerum CK: very highSteroid responsive | Muscle fibres: degeneration, regeneration. Endomysial connective tissue: increased. Endomysial capillaries: diffuse pathology, reduced number, enlarged, MAC deposition. Inflammation: minimal |
| Jo-1 antibodies | Onset: spring, adultWeakness: moderate, proximalFeatures: interstitial pneumonitis, Raynaud's, arthritisSerum CK: highSteroid responsive | Muscle fibres: perifascicular myopathy. Endomysial capillaries: normal. Perimysium: fragmentation. Inflammation: perimysial, macrophage |
| Paraneoplastic (necrotic) | Onset: acute, older adultWeakness: severe, proximalSerum CK: very highSteroid responsive | Muscle fibres: regional necrosis, MAC deposition in sarcoplasm. Inflammation: within muscle fibres; macrophage |
| Dermatomyositis | Onset age: child or adultWeakness: proximal > distalFeatures: rashSerum CK: highSteroid responsive | Muscle fibres: perifascicular atrophy. Endomysial connective tissue: normal. Endomysial capillaries: regional pathology, reduced number, enlarged, MAC deposition. Inflammation: perivascular, lymphocytic |
| Myositis + mitochondrial abnormalities | Onset age: older adultWeakness: quadriceps, slowly progressiveSerum CK: normal or mildly highSteroid resistant | Muscle fibres: focal invasion by inflammatory cells; cytochrome oxidase negative fibres. Inflammation: endomysial, lymphocytic |