Distal muscle involvement in granulomatous myositis can mimic inclusion body myositis.

The authors report on four patients aged over 50 with chronic myopathy suggestive of sporadic inclusion body myositis. They present progressive and selective weakness of the quadriceps femoris muscles. Asymmetrical and selective atrophy of the forearm muscles were noted in all, with more severe involvement of the flexors than the extensors. Biopsy revealed granulomatous myositis. Histological features of sporadic inclusion body myositis were lacking. Evidence for systemic sarcoidosis was found in one patient. Corticosteroid treatment was associated with a partial but significant improvement in two patients. Granulomatous myositis may mimic inclusion body myositis and may be steroid-responsive.