Facioscapulohumeral muscular dystrophy (FSHD; OMIM 158900) is among the most common forms of hereditary myopathy.1 At present, 2 genetically distinct disease subtypes, FSHD1 and FSHD2, are described2,3 on the basis of molecular features. The gene discussed is SMCHD1; the disease is facioscapulohumeral muscular dystrophy.