DMD and Duchenne muscular dystrophy: Although early studies did not find correlation between the longest and shorter isoforms [97, 98], it is now broadly accepted that pathogenic variants in the C-terminal portion of the dystrophin gene, affecting an increased number of isoforms, including the Dp140 and Dp71, in addition to the Dp427 isoforms, is associated with a higher prevalence and severity of intellectual disability among DMD/BMD individuals [71, 99].