Progressive Weakness and Rash

A 47-year-old man with hypercholesterolemia sought care for a 4-month history of progressive, proximal upper limb weakness and myalgia, followed by dysphagia, difficulty climbing stairs, and facial rash. Discontinuation of atorvastatin was of no benefit. Neurologic examination showed moderate weakness of the neck flexor muscles, shoulder girdle muscles, and finger extensors, and mild weakness of hip flexor and ankle dorsiflexor muscles. He had a heliotrope rash and Gottron sign. Serum testing showed an increased creatine kinase level. Needle electromyography showed myopathic changes with fibrillation potentials in proximal and axial muscles. Biopsy of the deltoid demonstrated a perifascicular pathologic process, including muscle fiber atrophy, and perivascular inflammatory exudate in the perimysium. Immunocytochemical studies showed patchy loss of intramuscular capillaries, some of which had complement (C5b9) deposition, and sarcoplasmic expression of myxovirus resistance protein A, mainly in the perifascicular regions. Immunologic testing was positive for autoantibodies to nuclear matrix protein 2 and negative for 3-hydroxy-3-methylglutaryl–coenzyme A reductase antibodies. Video swallow studies showed oropharyngeal dysphagia. Pulmonary function tests indicated mildly decreased maximal respiratory pressures but normal diffusing lung capacity for carbon monoxide. The findings were consistent with a diagnosis of dermatomyositis. The patient was started on oral prednisone and azathioprine, after checking for adequate thiopurine methyltransferase activity. Liver function tests and complete blood cell count with differential were assessed to monitor for potential azathioprine toxicity. Intravenous immunoglobulin was given. Follow-up examination revealed mild weakness of the shoulder girdle muscles after immunotherapy, and normal strength and creatine kinase value while on azathioprine monotherapy. Dermatomyositis is an idiopathic inflammatory myopathy. Idiopathic inflammatory myopathy is a group of autoimmune muscle diseases that includes dermatomyositis, polymyositis, inclusion body myositis, immune-mediated necrotizing myopathy, and overlap myositis, including antisynthetase syndrome.