FSHD2, representing less than 5% of patients with clinically defined FSHD, is not associated with deletions of D4Z4 copies but mutations of the SMCHD1 (on chromosome 18p11) or DNMT3B gene (on chromosome 20q11) in the presence of a disease-permissive 4qA haplotype [6,8,13]. This evidence concerns the gene SMCHD1 and facioscapulohumeral muscular dystrophy.