However, even long arrays result in FSHD symptoms in the presence of hypomethylation by mutation in the SMCHD1 gene (a condition termed FSHD2), whereas FSHD1 carriers of short but highly methylated repeat arrays may not manifest disease symptoms (Gaillard et al. 2014; Huichalaf et al. 2014). Here, SMCHD1 is linked to facioscapulohumeral muscular dystrophy.