The hypothesis that derepression of a regional transcript causes FSHD is further supported by individuals with the same clinical phenotype and decreased D4Z4 heterochromatin markings but without a contraction of the D4Z4 macrosatellite in the pathogenic range (FSHD2) [4], [5]. The gene discussed is SMCHD1; the disease is facioscapulohumeral muscular dystrophy.