PAX7 and facioscapulohumeral muscular dystrophy: Importantly, a refined 143 PAX7 target gene signature (termed the ‘FSHD muscle–blood biomarker’) in PBMCs correlated with widely used FSHD clinical severity scores defined in Ricci et al. 35 and Lamperti et al. 36 Investigation of our FSHD muscle–blood biomarker on an independent data set of 54 FSHD and 29 matched control blood samples validated it as a minimally invasive biomarker of FSHD severity, with particular relevance to older patients.