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Deletion of exon 46 and 47 means that a part of dystrophin gene is missing and hence, dystrophin protein can not be formed, resulting in Duchenne muscular dystrophy (DMD). There are totally 79 exons in dystrophin gene.
Exon skipping therapy in DMD is in experimental stage and early phase trials have shown promise. Phase II and III clinical trials need to show efficacy and safety, for it to be approved for clinical use.
In exon skipping therapy, an exon is removed so that the two ends of the dystrophin gene fit (in this case exon 45 may fit into exon 49, after exon 48 is removed/skipped), and dystrophin protein formation can be resumed.
I hope it helps.