In fact, the only real evidence that DUX4 protein is present in FSHD patient muscles is the misexpression of DUX4 target genes, which serves as a surrogate of DUX4 activity (Tawil et al., 2024; Wong et al., 2024; Wong et al., 2020; Yao et al., 2014). The gene discussed is DUX4; the disease is facioscapulohumeral muscular dystrophy.