Diagnosis of Duchenne dystrophy by enhanced detection of small mutations

Objective: To determine whether detection of small mutations of the dystrop hin gene can be increased using an enhanced method of single-strand conform ation polymorphism analysis. Background: Usual methods of DNA analysis for Duchenne dystrophy cannot identify mutations in one-third of cases. Muscle biopsy, with its inherent risks and added liability for patients with Duche nne dystrophy, becomes the sole method of diagnosis. Even with a tissue dia gnosis of dystrophin deficiency, many families are excluded from carrier de tection and prenatal diagnosis. Methods: Genomic DNA from a cohort of 93 pa tients with Duchenne dystrophy without identifiable gene mutations was scre ened for mutations. In each case, 22 kilobases of genomic DNA were scanned, including all 79 exons of the dystrophin gene, adjacent intronic regions, and six alternative exons 1. Results: Sixty-eight (73%) had small mutations , including 34 nonsense mutations, 27 microdeletions and insertions, and 7 splice site mutations. No missense mutations were found. One nonsense mutat ion in exon 59 was detected in four patients. Most mutations were new; 54 o f 62 different small mutations have not been reported. Mutations were found throughout the gene: 24% in the first quartile, 31% in the second, 16% in the third, and 29% in the fourth. Conclusions: A highly sensitive single-st rand conformation polymorphism method substantially increased detection of small dystrophin gene mutations and made it possible to diagnose approximat ely 90% of patients with Duchenne dystrophy by DNA analysis. These findings , combined with cost savings and safety issues, provide compelling reasons to consider DNA analysis as the initial diagnostic test for the suspected d ystrophin-deficient patient.