The pathogenesis of FSHD is that a reduced copy number of D4Z4 located at chromatin 4q35 results in reduced methylation and inhibitory heterochromatin levels in this region, which in turn promotes the abnormal expression of sequence‐specific transcription factor double homeobox 4 (DUX4) protein, a key factor to induce muscle atrophy in FSHD [87]. The gene discussed is DUX4; the disease is facioscapulohumeral muscular dystrophy.