SummaryThe dystrophin gene was analyzed in 59 Japanese patients with Duchenne muscular dystrophy (DMD) from 48 unrelated families, including 11 pairs of siblings, and three patients with Becker muscular dystrophy (BMD) from two unrelated families, including one pair of siblings. The relationship between the type of gene abnormality and clinical symptoms was examined. Twenty-seven of 50 (54.0 ~) unrelated DMD or BMD patients were found to have partial deletions, and five (10~o) appeared to have partial duplications in the dystrophin gene. Nine DMD patients, including three pairs of siblings, showed mental retardation, the existence of which was coincident in each pair of siblings, but deletion of an identical exon was not always related to mental retardation in unrelated patients.

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DNA samples from 21 unrelated Japanese patients with Duchenne muscular dystrophy (DMD) with nondeletion-type abnormality in the dystrophin gene and three samples from possible deletion carriers were analyzed using pulsed-field gel electrophoresis (PFGE). Among the 21 patients, 7 were found to carry partial duplications of the dystrophin gene spanning 50-400 kb. Of these 7 patients, 4 carried duplications corresponding to the major hot-spot regions for deletions (7.5-8.5 kb from the 5' end of cDNA), whereas two cases contained duplications in a region about 10 kb from the 5' end of cDNA, where causative mutations are reported to be rare. Only 1 case was found to contain a duplication of a region about 1 kb from the 5' end of cDNA, which is the reported duplication prone region. A combination of Southern blot analyses of conventional agarose gel electrophoresis and PFGE was confirmed to be useful, not only for detecting duplications and deletions, per se, but also for identifying carriers in the affected family.

We report two cases of ataxia telangiectasia in which a small number of T cells and a slightly diminished response to phytohaemagglutinin or concanavalin A were observed. In one case, serum IgA was undetectable. In spite of T and/or B cell involvement, natural killer activity and the percentage of natural killer cells determined by monoclonal antibodies Leu 7 were normal in both cases.