Myotonic dystrophy type 1 (DM1; MIM#160900) is a multisystem disorder caused by abnormal expansion of a CTG repeat in the 3′ untranslated region of the dystrophia myotonica-protein kinase gene (DMPK; MIM*605377)1–3. The gene discussed is WEE1; the disease is myotonic dystrophy type 1.