[Is chronic dermato- or polymyositis misdiagnosed as "weakness of old age"?]

Two women, aged 72 (case 1) and 77 (case 2) were referred for neurological diagnosis because of progressive muscular weakness, for 4 and 18 months, respectively, which had finally led to dysphagia and required mechanical ventilation. The cause of the disease in case 1 was classical dermatomyositis. Creatinine kinase concentration, never previously measured, was 950 U/l. In case 2 there was polymyositis, previously not considered as she had a diabetic polyneuropathy and muscle enzyme concentration was normal. In both cases the correct diagnosis was speedily confirmed by electromyography and muscle biopsy. Immunosuppressive treatment was largely successful in reversing the symptoms (case 1: initially 500 mg methylprednisolone daily, reduced to 50 mg daily within 6 weeks; case 2: 500 mg methylprednisolone daily for 1 week, then 100 mg daily plus 150 mg azathioprine with maintenance dosage of 20 mg glucocorticoid daily).--These two cases demonstrate that, particularly in the elderly, dermatomyositis and polymyositis should be considered in the differential diagnosis of progressive general weakness.