Despite causing potentially devastating effects in muscles of FSHD patients, and increased cell death when expressed in vitro, DUX4 expression is relatively rare (Kowaljow et al. 2007; Snider et al. 2009, 2010; Wallace et al. 2011; Ferreboeuf et al. 2014). This evidence concerns the gene DUX4 and facioscapulohumeral muscular dystrophy.