SMCHD1 and facioscapulohumeral muscular dystrophy 2: In humans, a deletion mutation (K274del) in SmcHD1 located at a conserved residue in the GHKL ATPase domain combined with a permissive 4q35 allele was suggested as a cause for Facioscapulohumeral muscular dystrophy type 2 (FSHD2) [37].