DUX4 and Facioscapulohumeral dystrophy: Facioscapulohumeral dystrophy (FSHD) is a progressive hereditary muscular dystrophy, caused by aberrant DUX4 expression.1 FSHD manifests in childhood in approximately 20% of patients.2 Early-onset FSHD, defined by facial weakness before age 5 and/or scapular weakness before age 10, is typically severe, with systemic features and more muscle weakness than classic-onset FSHD.2, -, 5 However, childhood FSHD can also present with milder phenotypes similar to adult-onset FSHD.6,7 Despite advancements in understanding adult FSHD,8,9 the natural history of childhood FSHD remains less explored.