While there is no clear correlation between the size of the deletion and the resultant clinical phenotype, the DMD vs BMD form can largely be predicted based on the “reading frame rule”: a severe, DMD phenotype is associated in ~ 90% of cases with out-of-frame pathogenic variants that induce a frameshift in the protein-coding sequence resulting in unstable RNA and subsequent nearly complete absence of dystrophin expression in muscles [163, 167]. The gene discussed is DMD; the disease is Duchenne muscular dystrophy.