Direct diagnosis of carriers of point mutations in Duchenne muscular dystrophy.

In about one-third of patients with Duchenne/Becker muscular dystrophy, the causative mutation does not involve gross alterations in the structure of the dystrophin gene. Prenatal diagnosis and carrier detection for such families is therefore dependent on the indirect method of linkage analysis with polymorphic DNA markers, a method that is subject to error. The identification of point mutations in the dystrophin gene in six affected males enabled us to develop direct assays, based on the polymerase chain reaction, that are specific for each of the mutations. In all six cases, the assays allowed us to offer families accurate carrier testing and prenatal diagnosis.