Dermatomyositis
An idiopathic inflammatory myopathy characterized by proximal muscle weakness and pathognomonic cutaneous findings. It is crucial to recognize because of its strong association with underlying internal malignancy.
Pathognomonic Skin Findings
- Gottron Papules: Violaceous, flat-topped, scaly papules over the dorsal aspects of the MCP, PIP, and DIP joints.
- Heliotrope Rash: Violaceous/lilac discoloration of the upper eyelids, often with associated periorbital edema.
- Shawl Sign: Photosensitive, erythematous eruption over the upper back and shoulders.
- V-sign: Erythema over the anterior neck and upper chest.
Diagnostic & Clinical Pearls
| Aspect | Details |
|---|---|
| Myopathy | Symmetric, proximal muscle weakness (e.g., difficulty rising from a chair or combing hair). |
| Malignancy Risk | High! Especially in older adults. Associated with ovarian, lung, and gastrointestinal cancers. |
High-Yield Exam Pearl:
- Anti-Jo-1 Antibody: Associated with the “antisynthetase syndrome” (myositis, interstitial lung disease, Raynaud phenomenon, and “mechanic’s hands”).
- Anti-Mi-2 Antibody: Highly specific for classic dermatomyositis with a better prognosis and excellent response to therapy.