Patient 2 was a 36-yr-old man presenting with progressive limb muscle weakness, which developed at the age of 20. Initially, he began to have a difficulty in raising his arm above his head and climbing stairs. The weakness was slowly progressive. His mother was noted to have similar symptoms (). His 34-yr-old brother and 39-yr-old sister were not affected clinically. The neurological examination was remarkable for moderate facial weakness; mild (MRC grade 4) and minimal weakness of proximal and distal extremity muscles, respectively; and humeral and quadriceps atrophy. Other remarkable findings included winged scapulae, anterior axillary folds, waddling gait, and hypoactive deep tendon reflexes. The serum creatinine kinase (CK) was 610 IU/L. The forced vital capacity (FVC) was 3.2 L (71% of predicted). Electrocardiogram, echocardiogram, audiogram, and nerve conduction studies were normal. Needle electromyography demonstrated chronic myopathic changes.
Patient 3 was an 18-yr-old man complaining of progressive right upper limb weakness over the prior 3 yr. The initial diagnosis was idiopathic right brachial plexopathy. He was a tennis player in his early teens. There was no family history of neuromuscular disease (). Clinical examination of his parents was normal. Remarkable neurological findings included mild bifacial weakness; mild (MRC grade 4) and minimal weakness of the right and left proximal upper limb muscles, respectively; winged scapulae in the right side; and hypoactive deep tendon reflexes. The serum CK was 750 IU/L. Other routine laboratory tests including thyroid function were normal. Audiogram, electrocardiogram, echocardiogram, and nerve conduction studies were unremarkable. The FVC was 4.2 L (98% of predicted). Needle electromyography revealed chronic myopathic changes.