SMCHD1 and facioscapulohumeral muscular dystrophy 2: Recently, mutations in human SMCHD1 have been shown to underlie type 1 and type 2 facioscapulohumeral muscular dystrophy (FSHD) (8, –, 10), with both types of the disease being dependent on the epigenetic silencing function of SMCHD1 at the D4Z4 repeat sequence.