OTC and Duchenne muscular dystrophy: Approximately two-thirds of boys have pathogenic missense or loss-of-function (stop gain, frameshift) variants in DAX-1/NR0B1, around one-sixth have a localized deletion of this gene on the X-chromosome (Xp21), and one-sixth have a larger Xp contiguous gene deletion syndrome that can involve genes causing glycerol kinase deficiency (GKD), ornithine transcarbamylase deficiency (OTC) and Duchenne Muscular Dystrophy (DMD) (47).