In the remaining 5% of FSHD patients (FSHD2, OMIM: 158,901), mutations in epigenetic modifier genes including SMCHD1, DNMT3B or LRIF1, a known SMCHD1 protein interactor, have been reported (Figure 2) (Lemmers et al., 2012; van den Boogaard et al., 2016; Hamanaka et al., 2020; Jia et al., 2021). The gene discussed is SMCHD1; the disease is facioscapulohumeral muscular dystrophy.