[A case of Down syndrome complicated with Becker muscular dystrophy].

A 22-year-old man with Down syndrome had a history of progressive muscular wasting which began at the age of 12 years. Serum CK level was elevated to 545 U/l (normal < 150) and muscle CT scan revealed patchy low density areas in the proximal muscles. A muscle biopsy specimen revealed marked dystrophic changes with patchy immunostaining for dystrophin. Multiplex PCR analysis of the genomic DNA extracted from peripheral blood lymphocytes disclosed a deletion of exons 45-47 of the dystrophin gene, confirming a diagnosis of Becker muscular dystrophy (BMD). This is the first report of Down syndrome complicated with BMD. Careful observation is required in detecting a coexistence of myopathy in mentally retarded patients.