The milder phenotype of the dystrophin gene double deletions

Objectives - This study aimed to examine the genotype-phenotype correlation in Duchenne muscular dystrophy (MD) patients with double deletion (Ddel) mutations in comparison with those having single deletions (Sdel). Materials and methods - The study included 250 Duchenne/Becker MD male patients from whom the 10 Ddel patients were compared with 20 Sdel subjects of same age and disease durations. The patients were subjected to neurological examination including functional disability grading scale (FDGS), molecular analysis of the dystrophin gene and immunohistochemical studies of some muscle biopsies. Results - The mean FDGS value in the Ddel group was lower than that in Sdel patients. The Ddel patients had partial expression of dystrophin in their skeletal muscles, while Sdel cases showed complete absence of the protein. Conclusion - Patients with double deletion mutations within the dystrophin gene have a milder phenotype than patients harboring single deletions at either major or minor hot spots of the gene.