Facioscapulohumeral muscular dystrophy (FSHD) type 2 is a hereditary muscle disease which can be caused by mutations in the SMCHD1 gene. While most SMCHD1 mutations are found in the DNA coding for the protein (exon), we here report FSHD-causing mutations in non-coding regions of the SMCHD1 gene (introns). This shows that these regions should be checked in FSHD diagnostics. Furthermore, we used CRISPR-Cas9 genome editing to remove an intronic SMCHD1 mutation from the genomic DNA in patient muscle cells. This restored levels of SMCHD1 protein, leading to reduced expression of the toxic FSHD causing DUX4 transcript. (By Remko Goossens, https://jmg.bmj.com/content/early/2019/10/31/jmedgenet-2019-106402 )