Also, a very homologous and equally polymorphic D4Z4 repeat is located on chromosome 10q26 (~ 98% similarity to the 4q35 locus), which has never been associated with FSHD [36] as this chromosome has no permissive single nucleotide polymorphism (SNP) in the DUX4 Polyadenylation Signal (PAS) (see “DUX4 gene expression”) [26]. Here, DUX4 is linked to facioscapulohumeral muscular dystrophy.