Each of these three CNVs contained one likely causative disease gene: SMCHD1, PMP22, or MTM1, involved in facioscapulohumeral muscular dystrophy-2 (digenic inheritence with the D4Z4 permissive haplotype), Charcot-Marie-Tooth disease 1A, and X-linked myotubular myopathy, respectively. Here, SMCHD1 is linked to X-linked myotubular myopathy.