DMPK and Adult onset: A drawback of early WES testing is its inability to identify the underlying genetic defects in two common adult-onset inherited myopathies: congenital myotonic dystrophy type 1 (CTD1) from DMPK repeat expansions and facioscapulohumeral muscular dystrophy (FSHD) due to contracted D4Z4 repeats on chromosome 4q35.