DNMT3B and facioscapulohumeral muscular dystrophy: In the other family, digenic inheritance of a heterozygous DNMT3B missense variant (c.2072C>T) and a permissive 4qA allele of 13 D4Z4 units induced hypomethylation at the D4Z4 repeat array but only one of the two family members was diagnosed with FSHD.