As described below, in FSHD, DUX4 has been associated with activation of pathways toxic to muscle tissue [50,65,66], including oxidative stress and DNA damage [67,68], inhibition of myogenic differentiation [67,69,70,71], impaired transcript quality control [54,72,73] and inflammation [40], leading to muscle cell apoptosis [67,74,75]. Here, DUX4 is linked to facioscapulohumeral muscular dystrophy.