[A 22-year-old man with long-standing weakness and atrophy predominantly in the lower extremities]

We report a right-handed 22-year-old man with muscle atrophy. His prenatal course and the delivery were uneventful, but he walked unsupported at 15 months of the age for the first time. He was apparently well but he was in the slowest group in running in schools. He noted a difficulty in climbing up stairs at 19 years of the age, and he was admitted to our hospital for the work up when he was 22-year-old. His family history and past medical history were unremarkable. On admission, he was a slender and tall guy in no acute distress. General physical examination was unremarkable, but he had high-arched palate and high-arched feet. On neurologic examination, mental status and higher cerebral functions were normal. Cranial nerves appeared intact, however, he had a thin and long face without weakness. The sternocleidomastoid muscles appeared somewhat atrophic and were moderately weak. He was able to walk normally, however, he needed a handrail when he went up stairs. Thigh muscles and triceps surae muscles were atrophic and slightly weak (4/ 5). Muscle tone was hypotonic and no deep tendon reflexes were elicited except for jaw jerk. No ataxia or involuntary movements were seen; sensation was intact. Laboratory examination was unremarkable except for slight increase in serum CK to 145 IU/L. An ischemic forearm exercise test revealed slight elevation of lactate and pyruvate in that base line levels were 5.4 mg/dl and 0.52 mg/dl, respectively, which rose to 11.4 mg/dl and 0.85 mg/dl, respectively, 20 minutes after the initiation of the ischemic exercise. The base line serum ammonia was 102.5 micrograms/dl which decreased to 64.8 micrograms/dl at 20 minutes. A diagnostic biopsy was performed from the left quadriceps femoris muscle. The patient was discussed in a neurologic CPC, and the chief discussant arrived at the conclusion that the patient had nemaline myopathy. Opinions were divided between nemaline myopathy and debranching enzyme deficiency. The results of the ischemic exercise was not typical of glycogen storage disease, but elevations of lactate and pyruvate did not appear to be sufficient to be interpreted as normal. Histologic examination of the biopsied specimen revealed marked type I fiber predominance and abundant nemaline rods. Cytoplasmic bodies were also seen. Histologic characteristics were consistent with the diagnosis of nemaline myopathy. The possibility of concomitant presence of AMP deaminase deficiency was discussed, because serum ammonia did not elevate in the ischemic exercise test.