DNMT3B and facioscapulohumeral muscular dystrophy: While most FSHD cases that are not attributed to D4Z4 contraction are caused by SMCHD1 mutations, FSHD has also been described in patients with mutations in the DNA methyltransferase 3 beta (DNMT3B) gene (FSHD4) and the ligand-dependent nuclear receptor interacting factor 1 (LRIF1) gene (FSHD3) (19, 20).