Pathogenic and nonpathogenic deletions in two families with Duchenne muscular dystrophy

Two deletions detected within the Duchenne/Becker muscular dystrophy (D/BMD) gene of normal male members of two DMD families were both independent, nonpathogenic deletions located in a large intron in the XJ region (DXS206) toward the 5' end of the gene [Burghes et al., 1987]. Investigation of the surrounding exons revealed no exon deletions or duplications. The simplest interpretation of these observations is that the deletions are entirely intronic and do not cause perturbation of the gene product, resulting in a normal phenotype. The disease phenotypes in the affected males in these two families are caused by exon deletions remote from this intron. Some caution is therefore indicated in using genomic deletions for clinical prediction.