The polymorphic repeat also encodes a member of the DUX gene family [11], [12] termed DUX4 which is supposed to have a major impact on the etiology of FSHD (Facioscapulohumeral muscular dystrophy;[13]–[15]), the third most common muscular dystrophy [16]. The gene discussed is DUX4; the disease is facioscapulohumeral muscular dystrophy.