Case 9: Differential Diagnosis.
Differential diagnosis includes post-denervation muscle hypertrophy, amyloid myopathy, malignant infiltration , sarcoid myopathy and skeletal muscle channelopathy.
EMG/NCV showed 3+ complex repetitive discharges in the right biceps with full motor unit interference pattern. Right upper extremity MRI (See below, top) demonstrated selective right biceps hypertrophy, edema and abnormal signal intensity on T2WI sequence. Biopsy of the R.biceps (See below, bottom) showed extensive chronic myopathic changes with some ongoing myofiber degeneration and regeneration with associated patchy mononuclear inflammatory infiltrates, consistent with focal myositis. There was no evidence for malignant or amyloid infiltrates or granulomatose disease. What is the diagnosis? (click here).
