Approximately 15% of disease causing mutations involve errors in alternative splicing. However, there is a case where an exon deletion enhances dystrophin production in muscle cells of DMD(Duchenne muscular dystrophy) patients. A deletion of exon 45 is the most frequent DMD-causing mutation. But some individuals with Beckner muscular dystrophy(BMD), a milder form of muscular dystrophy, have deletions in exon 45 and 46. Given that deletions often cause frameshift mutations, provide a possible explaination for the enhanced production of dystrophin in the presence of exon 45 and 46 deletions.