[A case of severe Becker muscular dystrophy diagnosed in early childhood--correlation between clinical severity and dystrophin testing].

Since the 14kb human Duchenne muscular dystrophy (DMD) cDNA was cloned and its protein product "dystrophin" was discovered, immunochemical, biochemical and genetic analyses of dystrophin (dystrophin testing) have provided an accurate diagnosis of DMD/Becker muscular dystrophy in the clinical field. We performed dystrophin testing for a 5-year-old boy and confirmed he had severe BMD. Multiplex PCR of the DMD gene showed in-frame type deletion from exon 45 to 48. Immunohistochemical analysis of the muscle specimen obtained from the patient showed a discontinuous and patchy staining pattern, using monoclonal antibody that recognizes the C-terminus domain of dystrophin. On immunoblot analysis, we detected a faint band of 390 kDa. Dystrophin quantity was less than 10% of that compared to normal controls. The correlation between clinical severity and dystrophin testing was discussed.