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Dermatomyositis and Polymyositis


- See:

      - Myopathic Disorders
- Ossification of Soft Tissue and Periosteum:

- Discussion:
- most common collagen vascular diseases which affect muscle;
- pts may be affected at any age;
- may be due to viral infection;
- in adults, note possible concomitant occult neoplasm;

- Clinical Findings:
- systemic illness;
- muscle and joint tenderness;
- progressive weakness which begins in proximal girdle;
- dermatomyositis:
          - look for skin involvement w/ heliotrope rash around eyelids & erythematous changes, especially over nail beds & knuckles;
- in contrast to systemic lupus, in which phalanges are involved & knuckles are spared, dermatomyositis will spare phalanges;
          - (Gottron's papules):
- multiple hyperkeratotic, erythematous, flat papules with central atrophy
- located on dorsum of the metacarpophalangeal and interphalangeal joints;

- Labs:
CPK & Sed rate are frequently elevated;

- EMG:
- EMG of myopathic disorders:
- useful for excluding neurogenic disorders;
- reveals short-duration, low-amplitude polyphasic units on voluntary activation;
- increased spontaneous activity with fibrillations & positive sharp waves;

    - polyphasic units of short & long duration may be present w/ chronic disease;

- Radiographs:
- types of dystrophic calcification: (see ossification of soft tissue)
- superficial masses (small circumscribed nodules) within skin;
- deep discrete subcutaneous nodular masses near joints that can impair movement (calcinosis circumscripta);
- deep linear sheetlike deposits within intramuscular fascial planes (calcinosis universalis);
- ref: Diffuse Soft-Tissue Calcinosis
- Treatment:
- steroid & immunosuppressive medications are useful


References

Diffuse Soft-Tissue Calcinosis

Review Article: Medical Progress: Polymyositis, Dermatomyositis, and Inclusion-Body Myositis.

Patterns of calcification in childhood dermatomyositis.