Myotonic dystrophy

Myotonic dystrophy (dystrophia myotonica, myotonia atrophica) is a chronic, slowly progressing, highly variable, inherited multisystemic disease. It is an autosomal-dominant disease.

It is characterized by wasting of the muscles (muscular dystrophy), cataracts, heart conduction defects, endocrine changes, and myotonia.

There are two main types of myotonic dystrophy. Myotonic dystrophy type 1 (DM1), also called Steinert disease, has a severe congenital form and an adult-onset form. Myotonic dystrophy type 2 (DM2), also called proximal myotonic myopathy (PROMM) is rarer than DM1 and generally manifests with milder signs and symptoms. Myotonic dystrophy can occur in people of any age. Both forms of the disease display an autosomal-dominant pattern of inheritance. Both "DM1" and "DM2" have adult-onset forms.

Signs and symptoms

Presentation of symptoms and signs varies considerably by form (DM1/DM2), severity and even unusual DM2 phenotypes. DM1 symptoms for DM2 include problems with executive function (e.g., organization, concentration, word-finding) and hypersomnia. Conduction abnormalities are more common in DM1 than DM2, but all people are advised to have an annual ECG. Both types are also associated with insulin resistance. Myotonic dystrophy may have a cortical cataract with a blue dot appearance, or a posterior subcapsular cataract.