DUX4 and Facioscapulohumeral dystrophy: Moreover, FSHD muscle biopsies with both high DUX4 target gene expression and robust PAX7 target gene score repression display more than twice the amount of histologically active disease compared to those with only high DUX4 target genes and minimal/no PAX7 target gene score repression, showing that DUX4 target genes are not the sole driver of disease.