Autosomal dominant FSHD1 is caused by abnormal expression of DUX4; FSHD2 shows digenic inheritance with alterations in genes associated with chromatin repression SMCHD1 and DNMT3B. Myotonic dystrophy is the most common adult onset muscular dystrophy and is inherited in an autosomal dominant pattern. Here, SMCHD1 is linked to myotonic dystrophy.