Occurrence:
(1) tends to be episodic, with each episode lasting a few weeks
(2) may present in a patient with or without a history of chronic sarcoid myositis
Clinical findings during an episode
(1) may affect one or multiple muscles
(2) presence of muscle tenderness and myalgia
(3) presence of proximal muscle weakness
(4) affected muscles may be swollen or show pseudohypertrophy
(5) may be accompanied by acute arthritis
(6) may be accompanied by erythema nodosum
(7) pulmonary function may be normal
Laboratory findings:
(1) elevated erythrocyte sedimentation rate (ESR)
(2) elevated serum creatine kinase
(3) angiotensin converting enzyme (ACE) activity may be normal
Electromyogram: abnormal, consistent with an inflammatory myopathy
Histologic findings: inflammatory myositis with noncaseating granulomas and myocyte degeneration
Differential diagnosis:
(1) deep vein thrombosis
(2) other forms of myositis
