Abstract Facioscapulohumeral muscular dystrophy (FSHD) is caused by the epigenetic derepression of the 4q-linked D4Z4 macrosatellite repeat resulting in inappropriate expression of the D4Z4 repeat-encoded DUX4 gene in skeletal muscle. In 5% of FSHD cases. D4Z4 chromatin relaxation is due to germline mutations in one of the chromatin modifiers SMCHD1. DNMT3B or LRIF1. https://www.knowall.blog/