Myotonic Dystrophy

DM1 – type1 myotonic dystrophy

Type 1 myotonic dystrophy is also sometimes called Steinert’s Disease. In common with other muscular dystrophies, it causes muscle wasting and weakness. However, it also affects many other systems in the body and symptoms can also include cataracts, heart conduction defects, endocrine changes including diabetes, and myotonia (prolonged muscle contractions or difficulty relaxing grip). This multi-systemic/multi-organ involvement is a particular feature of myotonic dystrophy, and in some cases, the non-muscle-related features of the condition – especially the heart problems – can be more of an issue for patients than the muscle weakness or myotonia.

The genetic change that causes the symptoms of myotonic dystrophy is present at birth, but depending on its severity, myotonic dystrophy symptoms may become noticeable at almost any age. The disease is often categorized according to age of onset.

Adult onset (“classical” form)

Less severe cases may not show any symptoms until adulthood. Adults who are moderately affected may have muscle weakness that gradually worsens with age, in addition to other symptoms such as excessive daytime fatigue, myotonia, diabetes, problems with breathing and swallowing, and sudden cardiac events. In mild cases muscle weakness will not usually have been a feature of early life, and adults with an extremely mild form of the condition may even have been active or athletic in their youth. Sometimes the diagnosis is made when the person concerned goes to the doctor for a symptom completely unrelated to muscle weakness, such as cataracts, or when a genetic test is done because another member of the family is more severely affected.

Congenital

Severe cases of myotonic dystrophy will be noticeable at birth, and babies with this “congenital” form may have breathing and swallowing problems and be quite severely ill, needing respiratory support and a feeding tube. Unlike some other forms of muscular dystrophy where infants may not achieve motor milestones, children with congenital myotonic dystrophy who overcome their initial breathing and feeding problems can make progress and often learn to walk, but as children they may have learning difficulties and other myotonic dystrophy symptoms.

Childhood onset

Children who have no problems at birth but who show symptoms in childhood may be described as having this form. Like the adult onset form it can cause muscle weakness and stiffness, but often it can also cause learning difficulties.

Management of myotonic dystrophy type 1

Although no ‘cure’ for myotonic dystrophy exists at present, adequate care and support can do a lot to help those affected. Many doctors are unfamiliar with the condition and this makes it particularly important that people who have myotonic dystrophy and their families are themselves aware of the problems they may face. Adults with myotonic dystrophy may not need to see a myotonic dystrophy specialist on a regular basis, but should receive follow-up as required. They should have treatment for any of the particular symptoms they do have – for example heart problems or diabetes – from a doctor who understands that these symptoms are related to their myotonic dystrophy. Whenever they see a new doctor they should explain that they have myotonic dystrophy. More information about management of myotonic dystrophy is available from the links below.

Genetics of myotonic dystrophy type 1

Myotonic dystrophy is inherited in an autosomal dominant pattern. It is caused when a certain segment of DNA at the end of a gene called the DMPK gene is abnormally repeated many times, forming an unstable region in the gene. This is called a triplet repeat expansion. Unaffected individuals have a small number of repeats (up to about 35) in this region, but in affected individuals the number can be much higher – rising to several thousand in congenitally affected children.

There is some correlation between number of repeats and severity of the disease, although individuals with a similar repeat count may be quite differently affected. There is also a correlation between number of repeats and age of onset, and a noticeable feature of myotonic dystrophy is that the number of repeats tends to increase in each generation – so a grandparent (slightly increased repeat count) might experience their first mild symptoms at age 60, while their children (moderately increased repeat count) notice symptoms at 30, and grandchildren (massively increased repeat count) may be congenitally affected. This phenomenon is known as “anticipation”. It does not always occur. The severe congenital form most often occurs when a mildly affected mother gives birth to a congenitally affected child due to a sudden large expansion in the repeat count.

DM2 – type 2 myotonic dystrophy

Type 2 myotonic dystrophy, also sometimes called ‘PROMM’ (proximal myotonic myopathy) is caused by a mutation in the CNBP gene – a different gene to that causing type 1 myotonic dystrophy. Type 2 myotonic dystrophy does not have a congenital or childhood onset form – it is only found in adults, with an age of onset generally between 30 and 60 years. People with DM2 may not have myotonia and do not usually have the same kind of facial muscle weakness or swallowing problems that are often seen in DM1. Weakness usually affects the proximal muscles (those closest to the trunk), and for many patients this is the most disabling feature later in life. It is quite common for DM2 patients to experience muscle pain (myalgia). Only a minority have cataracts. In common with DM1 patients, some DM2 patients may experience heart conduction defects and diabetes.

Genetics of myotonic dystrophy type 2

Like DM1, DM2 is caused by a “repeat expansion” in a segment of DNA in the affected CNBP gene. It is also inherited in an autosomal dominant pattern. Unlike DM1, it appears that the feature of “anticipation” (repeat count increasing with each successive generation) is not a feature of DM2. Prevalence of DM2 appears to vary in different populations and a higher prevalence has been observed in German populations.

Registry Publications – Summary Articles

The UK DM Patient Registry has been used as a tool to conduct research for a number of academic publications.  Below you will find summaries of these publications:

Title:  The UK Myotonic Dystrophy Patient Registry: facilitating and accelerating clinical research (download summary)

Title:  Benign and Malignant Tumors in the UK Myotonic Dystrophy Patient Registry (download summary)

Standards of care for adults with DM1

Myotonic dystrophy type 1 (DM1) is a severe, progressive genetic disease that affects between 1 in 3,000 and 8,000 individuals globally. No evidence-based guideline exists to inform the care of these patients, and most do not have access to multidisciplinary care centers staffed by experienced professionals, creating a clinical care deficit.

The Myotonic Dystrophy Foundation (MDF) recruited clinicians from the United States, United Kingdom, Canada, and Europe who have experience in the treatment of individuals living with DM1 to develop consensus-based care recommendations.

Consensus-based care recommendations for adults with myotonic dystrophy type 1.

http://dx.doi.org/10.1212/CPJ.0000000000000531

For more information please click here.

Standards of care for children with DM1

Standards of care for adults with DM2

About Clinical Research

Clinical research is medical research that is carried out on humans. Individuals volunteer to participate in studies that aim to uncover better ways to treat, prevent, diagnose and understand human disease.

Clinical research includes both clinical trials that test new treatments and natural history studies, which provide valuable information about how diseases progress.

If you are considering taking part in a clinical trial, the doctor in charge of the trial will give you a lot of information about the treatment being tested, the possible results and the possible side-effects. It is always worth finding out as much as you can before you agree to take part.

Even before you get to the stage of talking to a doctor about a specific trial, you can read a lot about the general principles of clinical trials online.

Two useful resources providing general information about clinical research created by the US National Institutes of Health (NIH) are provided below.

How does clinical research work?

Children and clinical studies

Finding out information about clinical trials

The most comprehensive online listing of trials is at www.clinicaltrials.gov: you can search for trials for a particular condition. We have also collected the listings of trials for specific diseases and you can find this in the “current trials” section in the menu on the left.

Muscular Dystrophy UK also has a listing of neuromuscular-related clinical trials in the UK and across the world available from the following link:

Muscular Dystrophy UK clinical trials listing

Further information
Clinical research: your questions answered – MDC publication
Neuromuscular clinical trials listing – MDC publication
How does clinical research work – NIH publication
Children and clinical studies – NIH publication

Current Trials in myotonic dystrophy

TREAT-NMD is working closely with the pharmaceutical companies planning trials in neuromuscular diseases. The resources and expertise available through the network can make it much easier for companies to carry out their trials.

Nevertheless, we cannot ourselves keep an up-to-date overview of all the trials that are currently happening across the world. The most comprehensive online listing of trials is at clinicaltrials.gov – companies are obliged to provide details of their trials there.

The table below lists all myotonic dystrophy trials registered or updated on clinicaltrials.gov in the last 1000 days. Because it links directly to clinicaltrials.gov it is automatically updated whenever the information on clinicaltrials.gov changes.

Please note that TREAT-NMD can take no responsibility for the accuracy of the information below, which is pulled directly from clinicaltrials.gov.