We identified muscle fibers with positive EPX staining in 2 out of 3 FSHD biopsies (Fig. 7A, B, E and F and Fig. S4A and C) in a pattern similar to the one previously described [48], whereas no EPX positive fibers were detected in the 4 healthy biopsies (Fig. 7C, D, G and H and Fig. S4B, D and E). The gene discussed is EPX; the disease is facioscapulohumeral muscular dystrophy.