In fact, some individuals with shorter dystrophin (due to large deletions involving multiple exons) have milder diseases compared with those with longer dystrophin.31 In addition, disease severity of dystrophinopathy is determined not by the size of the gene but rather by the quantity, as well as the quality, of the dystrophin protein produced. The gene discussed is DMD; the disease is neuromuscular disease caused by qualitative or quantitative defects of dystrophin.