Myotonic dystrophy

Myotonic dystrophy is a form of muscular dystrophy, a group of genetic disorders marked by progressive muscle loss and weakness. A hallmark is that muscles often cannot relax after contracting. Other features can include cataracts, intellectual disability and problems with the heart's conduction, and men may have early balding and infertility. It usually begins in the 20s and 30s, though it can appear at any age. Type 1 results from a mutation in the DMPK gene and type 2 from a mutation in the CNBP gene. It is typically inherited in an autosomal dominant pattern and tends to worsen with each generation, with type 2 generally milder. It was first described in 1909, and the cause of type 1 was determined in 1992. There is no cure, and treatment manages symptoms with supports such as braces, pacemakers and ventilation, while medicines such as mexiletine or carbamazepine can help relax muscles. It affects about 1 in 2,100 people.