Support and Resources for Myotonic Dystrophy Types I & II

Support Solutions for Myotonic Dystrophy in Europe

The Federation of European Myotonic Dystrophy Associations provides specialist support for people with Myotonic Dystrophy types I and II. Get in touch with our team of specialists for more information about our services.

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Myotonic Dystrophy Type I

Overview

Myotonic dystrophy type 1 (DM1), also known as Steinert’s disease, is the most common neuromuscular disease in adults (around 1/8000). It is an autosomal, dominant disorder caused by the expansion of a (CTG)n triplet repeat in the DMPK gene, located on chromosome 19.
The disease is characterized by a wide clinical spectrum and underlying molecular mechanisms, making it one of the most complex genetic disorders.

Symptoms

Symptoms include muscle weakness, myotonia, multiple endocrine disorders, respiratory insufficiency, heart issues (such as conduction problems and arrhythmias), eye problems, gastrointestinal tract issues, and brain-related complications. Cognitive dysfunctions compound the effects of other symptoms, making family and professional life difficult. The disease predominantly affects distal muscles.

The variability of symptoms is very high from one patient to another, even within the same family, ranging from a simple late-onset cataract to a congenital form with a poor prognosis early in life.

Anticipation: The disease is subject to amplification from one generation to the next, usually leading to increased severity of symptoms.

Research

Research is very active worldwide, with several highly promising molecules in development. Antisense oligonucleotides or gene-editing techniques (CRISPR) have demonstrated potential efficacy in targeting the genetic abnormality itself. However, at present, only symptomatic treatments are available.

Most countries have developed registries to better characterize the disease and facilitate research. The most advanced registry includes more than 3,800 patients in France.

Diagnostic

Myotonic Dystrophy Type II

Overview

Myotonic Dystrophy Type 2, also called Proximal Myotonic Myopathy (PROMM), is a rare genetic multi-system disorder of late childhood or adult onset, characterized by mild myotonia, muscle weakness, and, rarely, cardiac conduction disorders. It is an autosomal dominant disorder caused by the expansion of a (CCTG)n quadruplet repeat in the CNBP gene located on chromosome 3. Its prevalence is low (approximately 1 in 100,000) but appears to be higher in countries like Germany and the United States.

Symptoms

DM2 typically manifests in adulthood and presents with variable symptoms, such as early-onset cataracts (before age 50), varying degrees of grip myotonia, thigh muscle stiffness, muscle pain, and weakness. There is no congenital form.

Symptoms usually begin between the second and sixth decades of life (median age: 48 years). Early in the disease, mild weakness is observed in hip extension, thigh flexion, and finger flexion.

Extensive pain is frequently reported in DM2 and includes abdominal, musculoskeletal, and exercise-related pain. The pain tends to fluctuate without an obvious cause, varying in intensity and distribution across the limbs. It may share characteristics with fibromyalgia, and a prior diagnosis of fibromyalgia is relatively common.

Cardiac issues are generally less severe and frequent in DM2 than in DM1. Clinically significant cardiac features in DM2 include arrhythmias, atrioventricular conduction defects, and, in some cases, overt dilated cardiomyopathy. A high prevalence of atrial fibrillation and left ventricular dysfunction has also been reported in DM2 patients.

Unlike DM1, ventilatory insufficiency has not been reported in DM2.

The cognitive impairment associated with DM2 is similar to, but less severe than, that seen in DM1. Cognitive abnormalities, a reduction in cerebral blood flow in the frontal and temporal poles, and occasional white matter alterations in the brain have been observed.

Other symptoms, such as hypogonadism, glucose intolerance, excessive sweating, and dysphagia, may also occur and tend to worsen over time.