Deletion proximal to DXS68 locus (L1 probe site) in a boy with Duchenne muscular dystrophy, glycerol kinase deficiency, and adrenal hypoplasia.

We report a case of a boy with Duchenne muscular dystrophy (DMD) associated with GK deficiency (GK), congenital adrenal hypoplasia (AHC), and mental retardation. Cytogenetic analysis of prometaphasic chromosomes revealed an interstitial chromosome deletion at Xp21.2 possibly extending to Xp21.1 or Xp21.3. His phenotypically normal mother was heterozygous for this deletion. DNA probe analysis on Southern blots showed that the deletion affected the following probe sites: 754, pERT 84, 21A, XJ2.3, pERT 87, JBir, and J66-H1, whereas L1, C7, and CX5.4 probes gave a normal signal. Pulse field gel electrophoresis after SfiI digestion did not show abnormal fragments with L1. These data are consistent with a deletion of about 4 megabases and indicate that the GK and AHC loci are proximal to L1 and distal to J66-H1.