5 Interesting Facts of Idiopathic Inflammatory Myopathies
1. Polymyositis (PM) and dermatomyositis (DM) are characterized by proximal muscle weakness, elevated muscle enzymes, and an abnormal electromyogram and muscle biopsy.
2. The typical skin manifestations of DM include heliotrope rash, Gottron’s papules, and abnormal nailfold capillaries. Skin ulcerations and anti-transcription intermediary factor 1 (TIF-1)γ (p155/140) antibodies signal the presence of an associated underlying malignancy.
3. Myositis-specific autoantibodies (MSAs) can predict extramuscular manifestations, response to therapy, and prognosis.
4. The antisynthetase antibody (ASA) syndrome is characterized by myositis, interstitial lung disease (ILD), arthritis, mechanic’s hands, fever, and Raynaud’s phenomenon.
5. Inclusion body myositis (IBM) should be considered in patients aged over 50 years with proximal and distal muscle weakness, neuropathic features, and poor response to steroid therapy.