The up-regulation of the last DUX4 gene in individual showing a reduced numbers (≤8) of D4Z4 repeats at 4q35 combined with a specific molecular signature (4A(159/161/168) DUX4 polyadenylation signal (PA) haplotype) is supposed to underlie FSHD pathophysiology [6]. This evidence concerns the gene DUX4 and facioscapulohumeral muscular dystrophy.