DUX4 and facioscapulohumeral muscular dystrophy: As a result, it is currently infeasible to use DUX4 expression as a clinical biomarker for FSHD, although there has been considerable effort to identify and detect DUX4-associated biomarkers for use as an indirect indication of DUX4 gene expression (Yao et al. 2014; Rickard et al. 2015; Eidahl et al. 2016; Jagannathan et al. 2016; Heuvel et al. 2018).