Intrafamilial variability in dystrophin abundance correlated with difference in the severity of the phenotype.

In Duchenne muscular dystrophy, the progression of the disease is always severe and predictable, while in Becker dystrophy there is a wide variability (intra and inter familial) in the severity of the phenotype. We report here a family in which the proband, who is currently 15 years old, is showing a severe DMD progression, while his affected maternal uncle, aged 29, has a more benign course, compatible with BMD. No DNA deletion was detected in both patients. Dystrophin analysis through immunofluorescence and western blotting showed a negative pattern in the youngest patient and a positive one in the oldest. Apparently, this is the first report on intrafamilial variability in dystrophin abundance correlated with a difference in the severity of the phenotype.