DNMT3B and Facioscapulohumeral dystrophy: There are two genetic causes of FSHD [16]: FSHD1, which represents ~ 95% of FSHD cases, is caused by a loss of D4Z4 repeat copy number from 8–100 to 1–10 copies [17, 18], and FSHD2 (~5% of cases) which is due to mutation of epigenetic regulators, such as Structural Maintenance of Chromosomes flexible Hinge Domain Containing 1 (SMCHD1) (>95% of FSHD2 cases), its binding partner Ligand Dependent Nuclear Receptor Interacting Factor 1 (LRIF1), or DNA methyltransferase 3 beta (DNMT3B) [19–21].