Fusion indexes and myogenic expression levels at Day 5 of differentiation were also similar in genetically matched immortal muscle cell clones from a mosaic FSHD1 patient72 and FSHD and control human myoblasts.73 We detected DUX4 and ZSCAN4 expression in affected myotubes only. This evidence concerns the gene ZSCAN4 and facioscapulohumeral muscular dystrophy.