Germinal mosaicism in a sample of families with Duchenne/Becker muscular dystrophy with partial deletions in the DMD gene.

Germinal mosaicism should be considered when estimating the recurrence risk in families with Duchenne/Becker muscular dystrophy (D/BMD). Germinal mosaicism, however, has not been assessed in Mexican families with deletions in the DMD gene. To determine the distribution of deletions in the two hot spots and the proportion of de novo and transmitted deletions, we analyzed 153 individuals with D/BMD and a DMD partial deletion and 322 of their maternal female relatives. Predilection for the distal hot spot was observed in 112 families (73%), while gene dosage analysis of female relatives of D/BMD patients identified germinal mosaicism deletions in at least 11.6% of the patients' families, thought to result from de novo mutations. Recurrence risk due to germinal mosaicism justifies carrier detection in maternal female relatives and prenatal diagnosis in mothers of individuals with apparently de novo DMD deletions.