Myotonic dystrophy type 2 (DM2), also called proximal myotonic myopathy (PROMM), is a genetic condition that typically affects the skeletal muscles, which are used for movement. It also commonly affects other bodily functions including the heart, lungs, and gastrointestinal system. DM2 leads to progressive muscle weakness and muscle wasting over time.

There are two main types of myotonic dystrophy. Myotonic dystrophy type 1 (DM1), which tends to be more severe and common in the UK, and DM2. For more information on DM1, see our DM1 page.

Myotonic dystrophy type 2 (DM2) can affect people in several ways, with symptoms usually starting in adulthood. Unlike DM1, there is no congenital (from birth) form of DM2.

Skeletal muscles

In DM2, muscle weakness tends to start around the thighs, hips, and upper arms. This can make it hard to climb stairs, stand from a seated position, or lift objects. Weakness in the hips and thighs can also affect walking and balance. Many people with DM2 also feel muscle pain, which can feel like aching or cramping. The weakness usually worsens slowly. Some people may only have mild symptoms, while others might need walking aids. Facial weakness is often mild or not present in DM2, unlike DM1, where it is often the first sign.

Myotonia (muscle stiffness) is also a symptom of DM2. It makes it hard to relax muscles, especially in the hands and jaw. Myotonia can usually be improved by activating and using the muscles repeatedly, a process called the ‘warm up phenomenon’. Myotonia can also be managed with medication if necessary.

Pain

People with DM2 often experience pain in the muscles, joints, spine, and ligaments. This is especially felt in the region of the neck, back, shoulders, hips, and upper legs. The pain can change from day to day. Muscle weakness, fatigue, and certain medications (such as statins) can make the pain worse.

Cardiac

DM2 can affect the heart’s electrical system and people may develop arrhythmias (irregular heartbeats). Symptoms can include dizziness, chest pain, trouble breathing, and fainting. Heart problems can begin even when muscle weakness is mild, and some people may not have noticeable symptoms when they start. Regular heart check-ups are important to identify any issues early and manage them with treatment.

Respiratory

In DM2, weakness and stiffness in the muscles that help with breathing can affect respiratory function and make it harder to breathe efficiently, especially when sleeping at night. This can lead to respiratory insufficiency, where the body can’t maintain normal levels of oxygen and carbon dioxide in the blood. The central nervous system, which is made up of the brain and spinal cord, helps control how the muscles used for breathing work. This can be especially important during sleep.

People with DM2 may experience fatigue and excessive daytime sleepiness (EDS) which an impact their quality of life. Respiratory muscle weakness can also make it harder to cough effectively and clear mucus from the lungs, leading to frequent chest infections and aspiration pneumonia (a serious lung infection). General anaesthesia and some types of pain medications can further contribute to respiratory problems.

Gastrointestinal

Gastrointestinal symptoms are common in DM2 and can range from mild issues like indigestion to more severe bowel problems. Many people with DM2 experience slow digestion, which can cause bloating and discomfort. There is often a reduced ability for the digestive tract to move food efficiently, causing symptoms like bloating and abdominal pain. These symptoms are often like irritable bowel syndrome (IBS), and constipation and diarrhoea are common.

People often have high levels of GGT and liver enzymes, which don’t usually indicate liver problems but need to be closely monitored.

Swallowing difficulties (dysphagia) are common but often go unnoticed. These issues can lead to coughing and choking when eating or drinking, the feeling of food sticking in the throat, and unplanned weight loss. It may be difficult to take in enough nutrition. Swallowing difficulties can cause frequent chest infections and aspiration pneumonia, which needs to be treated quickly.

Endocrine

The endocrine system controls the hormones in our body that affect metabolism and other functions. People with DM2 are more likely to have issues with this system. This can lead to conditions like type 1 and type 2 diabetes, hypothyroidism (an underactive thyroid), adrenal insufficiency (when the adrenal glands don’t produce enough hormones), and problems with fertility and sexual function. The frequency and severity of these issues can vary from person to person. An endocrinologist, a doctor who specialises in hormone-related health, can help manage these conditions and recommend the best therapy, if needed.

Eyes

People with DM2 often develop cataracts (clouding of the lens in the eye) before the age of 50. They develop slowly and may not cause noticeable symptoms such as blurry vision until they get worse. Early onset cataracts can be effectively treated. Some people may have a history of cataracts at an early age and then develop muscle symptoms later in life. Other eye problems include squints, droopy eyelids (ptosis) and difficulty fully closing the eyelids, which can lead to dry eyes. Changes in the retina (the light-sensitive layer at the back of the eye) and changes in eye pressure can also occur. Annual eye tests are recommended to identify and manage these conditions.

Cognition

DM2 can affect the brain, but this is generally less noticeable than in DM1. Some people may experience mild cognitive and neurological challenges such as difficulty with concentration, memory, decision-making, organisation, and planning. People may also experience mental health issues such as apathy and depression. Mental health services can provide advice on the best therapy, if needed.

Sleep problems are common and can cause excessive daytime sleepiness (EDS), where staying awake during the day becomes difficult. EDS can be managed with medications if needed, following a heart and lung health check. This may be linked to changes in the brain areas that control sleep and breathing.

Genetic changes

DM2 was recognised as a separate condition from DM1 in the 1990s, when researchers found that some people had symptoms like DM1 but did not have the same genetic change seen in DM1.

DM2 is caused by a change in the CNBP gene, which is found on chromosome 3. This change leads to an abnormal increase in a repeated section of genetic code, known as CCTG repeats. In people without DM2, this CCTG sequence repeats fewer than 75 times. In people with DM2, the number of repeats is much higher.

When the number of CCTG repeats gets too high, it disrupts how the cells work and causes muscle weakness and other symptoms. Unlike DM1, the number of repeats does not clearly determine how severe the symptoms are.

Inheritance

DM2 is inherited in an autosomal dominant pattern. This means a person needs to inherit the genetic change from one parent for the condition to develop. DM2 doesn’t tend to get worse in each successive generation. Most people with DM2 have a parent with the condition, though their symptoms may be very mild. It’s recommended that doctors assess the whole family to see if others are affected.

There are some rare cases where DM2 appears without a known family history.

For more information, see our inheritance and genetics page.

A GP can make a referral to a neurologist, a doctor who specialises in conditions that affect the muscles and nervous system. A neurologist can come to a suspected diagnosis of DM2 based on a combination of clinical symptoms, a physical examination, and family history. To confirm the diagnosis, genetic testing can be done using a blood sample. This test looks for an unusually high number of CCTG repeats in the CNBP gene. Typically, more than 75 repeats are linked to clinical symptoms, while less than 28 repeats are considered normal. People with repeats between 28 and 75 may or may not experience symptoms of the condition.

For more information, see our diagnosis page.

Access to healthcare team

People with DM2 should have access to a multi-disciplinary healthcare team to monitor symptoms. Usually, the lead professional will be a neurologist in a specialist neuromuscular clinic. If you do not have contact with a neurologist or specialist doctor, ask your GP.

Cardiac management

It’s usually recommended to have an electrocardiogram (ECG) each year with a GP or cardiologist, a doctor who specialises in heart problems, to detect heart issues early. Sometimes, extra tests such as an echocardiogram (ECHO) and Holter monitoring may be needed if a problem is suspected or found. In some cases, an electrophysiological study (EPS) may be done to evaluate the heart’s electrical system and check for abnormal heart rhythms. In the case of atrial fibrillation (an uneven heartbeat), a treatment called ablation might be recommended to help maintain a normal heart rhythm. For other heart rhythm problems, a small device called a pacemaker, or an implantable cardioverter-defibrillator (ICD) might be needed.

Respiratory management

It’s important to monitor respiratory health, especially if there are symptoms like shortness of breath or frequent chest infections. Lung function can be checked with tests like forced vital capacity (FVC) and peak cough flow (PCF) at review appointments. Overnight sleep studies may also be necessary to assess breathing while sleeping. If needed, breathing exercises, cough assist devices, and non-invasive ventilation (NIV) may be recommended to support respiratory function. If someone has Excessive Daytime Sleepiness (EDS), a medication called modafinil may be considered if central hypersomnia is suspected.

Pneumococcal, annual flu, and COVID-19 vaccinations should be kept up to date.

Exercise and physiotherapy

Staying active and maintaining strength is important, and a physiotherapist can help create a suitable exercise plan. A physiotherapist is a healthcare professional who helps manage symptoms through movement, exercise, and manual therapy. Regular stretching to keep muscles flexible and prevent tightness across joints, strengthening exercises to prevent muscle weakening, and low-impact aerobic exercise such as walking and swimming to support heart and lung health are recommended. After exercise, time should be allowed to fully recover the next day. Some muscle soreness is okay, but this should not be severe pain and should improve over time. To find out more about advice for adults, see exercising with a muscle wasting condition. Orthotics such as insoles, braces, splints might be recommended by a physiotherapist to help with instability. Walking sticks may be useful for extra support and help with balance. Aids, such as rollator, wheelchair, mobility scooter, may be helpful as the condition progresses and chair-based exercises can be provided.

Pain management

Usually pain in DM2 is managed with non-steroidal anti-inflammatory drugs (NSAIDs), like Ibuprofen, to reduce the pain and inflammation. Opioids (stronger painkillers) should be used with caution and in low doses to monitor for any side effects [see surgeries and anaesthesia guidelines below] . A doctor must guide the use of these medications. In cases where pain isn’t relieved by NSAIDs, people may be referred to a physiotherapist. The physiotherapist can suggest strengthening exercises and may recommend using orthoses or braces to reduce pain.

Gastrointestinal management

Gastrointestinal issues can significantly impact daily life. Management of gastrointestinal symptoms such as constipation, diarrhoea, and bloating are essential. Diarrhoea or constipation might improve by following a high fibre diet, with increased water intake, and establishing a toilet routine. Medication can be used to treat gastrointestinal symptoms. Severe constipation not responding to laxatives or suppositories may need assessment to exclude other causes or gut dysmotility. Chronic diarrhoea also requires investigation.

With regards to swallowing management, speech and language therapists can provide strategies to avoid complications while eating and drinking, such as sitting upright, careful chewing, and avoiding talking while eating. Swallowing therapy is usually offered to maintain as much swallowing function as possible. If swallowing difficulties are severe and cause unplanned weight loss, a dietitian can advise on adapting or supplementing the diet and explore other options such as a feeding tube if necessary.

Care recommendations

For more details on best practices in managing DM2, including detailed recommendations for monitoring, treatment, and supportive care, refer to the Consensus-based Care Recommendations. These recommendations were published in 2019 by the Myotonic Dystrophy Foundation (MDF) and created with leading myotonic dystrophy clinicians based in Europe, the US, and Canada.

• Consensus-based Care Recommendations for Adults with DM2

Anaesthesia stops a person feeling pain during a procedure or surgery. People with DM2 have a higher risk of complications during procedures with general anaesthesia. This can be because of heart and breathing issues. It’s crucial that the anaesthetist and surgical team are aware of a diagnosis of DM2 and any cardiac and respiratory complications. A pre-operative assessment and extended post-operative monitoring is necessary. Specialist neuromuscular clinics can be contacted for advice if needed. As every person with DM2 is unique, all situations should be assessed individually to provide the safest approach.

For more information, see the Practical Suggestions for the Anesthetic Management of a Myotonic Dystrophy Patient guide.