Clinical Reasoning: A 33-year-old man with cardiomyopathy and myopathy

Abstract

An 18-year-old Hmong man sought medical care because of worsening performance on military training exercises. He had a previous syncopal episode with prompt recovery. His medical and developmental history were otherwise unremarkable. A chest radiograph revealed cardiomegaly and, after further cardiac tests, he was diagnosed with postinfectious or idiopathic cardiomyopathy. His cardiac function deteriorated and heart transplantation was pursued. During preoperative evaluation, his serum creatine kinase (CK) was noted to be persistently elevated in the 4,000s, prompting further investigation, but since he was not weak or otherwise symptomatic, definitive diagnosis and treatment were not pursued. When 19 years old, he underwent orthotropic heart transplantation. In the following years, he had multiple stents placed for coronary artery disease and developed type 1 diabetes mellitus, but he worked as an information specialist and cared for himself.In the patient's early 30s, family members noticed a limp, and he perceived an inability to walk on the toes of the left foot. He also experienced burning of his legs after moderate activity, such as climbing 2 flights of stairs. The statin he took for hyperlipidemia was discontinued. These symptoms, along with persistent hyperCKemia, prompted a neurology consultation. He denied muscle weakness, cramps, episodes of paralysis, or urine discoloration. There was no family history of muscle disorder, weakness, cardiomyopathy, or sudden death. Examination demonstrated mild weakness (4/5 on Medical Research Council scale) of neck flexion, elbow flexion, and shoulder external rotation, more prominent on the left. He could not stand on his toes. He had bilateral, asymmetric atrophy of the posterior calves, left more than right. Tone was normal, and there was no percussion or grip myotonia. Reflexes were 21 and symmetric in triceps, brachioradialis, and patella, 11 at the right biceps, absent at the left biceps, and absent at both ankles. He had normal mental status, cranial nerves, sensory examination, and coordination. EMG revealed widespread abnormal spontaneous activity involving upper and lower limbs, as well as thoracic and lumbar paraspinal muscles with complex repetitive or pseudomyotonic discharges. Volitional activation revealed early recruitment of small, short-duration, polyphasic motor units. Questions for consideration: