Patient 1 was a 30-yr-old woman complaining of progressive limb muscle weakness. She was in good health until age 12 yr, at which time she began to have a difficulty in raising her right arm above her head. Later, she developed increasing difficulties climbing stairs. By report, her mother had similar symptoms from the age of 40. His 35-yr-old brother was not affected clinically (). The neurological examination was remarkable for moderate facial weakness; moderate (Medical Research Council [MRC] grade 3) and mild (MRC grade 4) weakness of proximal upper and lower limb muscles, respectively; humeral atrophy; anterior axillary folds; winged scapulae; waddling gait; and hypoactive deep tendon reflexes. The serum creatine kinase (CK) was 233 IU/L (normal, <270 IU/L). Other routine laboratory tests including thyroid and parathyroid function were normal. Audiogram, electrocardiogram, echocardiogram, nerve conduction studies were unremarkable. Needle electromyography showed chronic myopathic changes in the left deltoid, biceps brachii, and vastus lateralis muscles. A muscle biopsy from the right vastus lateralis revealed marked fiber size variations, increased internalized nuclei, endomyseal fibrosis and fat ingrowth, and frequent lobulated myofibers.
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.