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.     



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Wednesday, November 30, 2016 2:40 pm