The study of van den Boogaard et al. [21] showed that in one family carriers of the heterozygous DNMT3B missense variant (c.1579T>C) had reduced DNA methylation levels at the D4Z4 repeat array and were more likely to develop FSHD in comparison to other family members carrying an identical permissive 4qA allele of 9 D4Z4 units. The gene discussed is DNMT3B; the disease is facioscapulohumeral muscular dystrophy.