The overwhelming majority of FSHD cells have no detectable levels of DUX4 target gene expression; with only 19.7% identified using the full Yao et al. (2014) DUX4 biomarker (30), while van den Heuvel et al. (2019) (32) reported only 0.4% of FSHD cells expressed ≥5 DUX4 target genes using a 67 gene subset of their full Yao et al. (2014) (30) DUX4 target gene signature. Here, DUX4 is linked to facioscapulohumeral muscular dystrophy.