[Four siblings with becker muscular dystrophy (BMD) manifesting severe mental retardation]

A 33-year-old man with BMD manifesting severe mental retardation is reported. This patient has mild pseudohypertrophy in his calf muscles and showed an elevation of creatine kinase (CK) level in the serum (2215 IU/L). He was diagnosed as autistic at the age of three. His intellectual level was estimated to be two years old in social intelligence and four months old in speech ability at the age of 33. However his muscle strength remains within the normal range. All of his three siblings have similar symptoms, such as severe mental retardation and elevated CK level in the serum (1735-3641 IU/L) and lack apparent muscular weakness. Gene analyses by multiplex PCR and Southern blotting showed all of the siblings had the deletion of exon 4 in the dystrophin gene. Pathological findings of a muscle biopsy specimen showed a mild irregular dystrophin stain of the muscle surface membrane. This is a rare familial case of Becker muscular dystrophy manifesting severe mental retardation with scarce muscular weakness.