Rarely, FSHD can also result from mutations in genes encoding D4Z4-binding chromatin modifiers, such as SMCHD1, DNMT3B, or LRIF1, in combination with at least one 4qA D4Z4 allele of typically 8–20 RU (FSHD2; MIM 158901) [4–6]. The gene discussed is SMCHD1; the disease is Facioscapulohumeral dystrophy.