Early onset distal muscular dystrophy

A 14-year-old Chinese boy, who first became aware of muscle weakness in the lower limbs at 6 years of age, had progressive distal muscle weakness and atrophy, predominantly in the lower leg muscles. He exhibited reduced ankle dorsiflexion and tended to walk on his toes, showing preferential anterior tibial muscle involvement. Laboratory examination revealed a moderately elevated serum creatine kinase level of 905 IU/l. Computed tomographic scanning of muscle disclosed low density areas in the lower legs. A muscle biopsy specimen from the biceps brachii revealed mild dystrophic changes. We made a diagnosis of distal muscular dystrophy based on these findings, but could not classify it as one of the previously reported forms. The symptoms mimicked those of tibial muscular dystrophy, though the onset of the disease is far earlier than the previously described ones of distal muscular dystrophies. It remains unknown whether this patient has a new type of distal muscular dystrophy, or a variant form of the Miyoshi type or tibial muscular dystrophy.