A Guide for Patients and Families

What is... Myotonic Dystrophy

Myotonic dystrophy (DM) is a Type 1 DM (DM1) occurs when a gene on musculoskeletal disorder that chromosome 19 called DMPK contains affects the muscles and a number an abnormally expanded section. of different organs in the body. Type 2 DM (DM2) is caused by an DM is the most common form of abnormally expanded section in a gene muscular dystrophy that begins in on chromosome 3 called ZNF9. adulthood, usually in the 20s or 30s. In some cases, babies are born with a It is a genetic disorder characterized by variation of myotonic dystrophy type 1 progressive muscle loss and weakness. called congenital myotonic dystrophy.

DM is inherited in an autosomal DM causes weakness of the voluntary dominant manner, which means it muscles, although the degree of weakness takes the mutated (flawed) gene from and the muscles most affected vary only one parent to cause the disease. greatly according to the type of DM and the age of the person with the disorder. There is no cure for DM, but medications and therapy can help DM is classified into two types, manage some of its symptoms. type 1 and type 2, each of which may affect different muscles.

People with DM often experience prolonged muscle tensing (myotonia) and are not able to relax certain muscles after use. For example, someone with DM may have difficulty letting go of someone’s hand after shaking it.

The severity of the disease may vary, even among members of the same family. However, in general, symptoms tend to progress slowly. What are the signs and symptoms of DM? DM is a multi-system condition affecting many parts of the body. The symptoms in people with DM2 tend to be milder than in those with DM1, but the symptoms may overlap. People with DM1 typically experience involvement of the legs, hands, neck, and face, while individuals with DM2 typically experience involvement of the neck, shoulders, elbows, and hips.

Nervous system Skeleton and muscle • Cerebral atrophy • Hypotonia • Developmental delay • Muscle weakness • Excessive daytime sleepiness • Muscle stiffness • Facial diplegia • Muscle tightness Cognition • Muscle wasting • Intellectual disability • Myalgia • Learning disability • Myotonia • Obsessive-compulsive traits Heart Gastrointestinal • Cardiac conduction defects • Dysphagia • Cardiomyopathy • Feeding difficulties in infancy • Palpitations • Tachycardia Hormonal/sexual • Complicated pregnancy Respiratory system • Male baldness • Breathing difficulties • Male infertility • Low sperm count Endocrine • Testicular degeneration • Diabetes

8 Life expectancy may be reduced for people with DM1. An increased risk of What should I know about DM? death may be associated with younger age of onset, more severe muscle 1 Overall intelligence is usually 4 The childhood-onset form of DM1 — begin- weakness, and cardiac conduction normal in people with DM, but ning after infancy but before adolescence defects. People with more mild learning disabilities and an — is more often characterized by cognitive symptoms of DM1 may have a apathetic demeanor are and behavioral abnormalities than by normal lifespan. common in the type 1 form. physical disabilities. Eventually, muscle symptoms develop, to varying degrees. 9 DM2 is, in general, a milder disease 2 Generally, the earlier DM1 be- than type 1. It does not appear to have a congenital-onset form and rarely gins, the more profound the 5 The most common type of DM1 — the begins in childhood. symptoms tend to be. In con- adult-onset form — begins in adolescence genital DM1, which affects or young adulthood, often with weakness in children from the time of birth, the muscles of the face, neck, fingers, and 10 In contrast to type 1 DM, the muscles there can be serious impairment ankles. The weakness is slowly progressive affected first in DM2 are the proximal of cognitive functioning. These for these and eventually other muscles. children also may have prob- muscles — those close to the center lems with speech, hearing of the body — particularly those around the hips. However, some finger and vision. 6 As the disease progresses, the heart can weakness may be seen early as well. develop an abnormal rhythm and the heart The disorder progresses slowly, but muscle can weaken. The muscles used for mobility may be impaired early because 3 Children with congenital-onset breathing can weaken, causing inadequate of weakness of the large, weight-bear- DM1, once they survive the breathing, particularly during sleep. crucial neonatal period of ing muscles. respiratory muscle weakness with the help of assisted 7 In DM1, the involuntary muscles, such 11 Definitive information about prognosis ventilation, usually show as those of the gastrointestinal tract, in people with myotonic dystrophy type improvements in motor and can be affected. Difficulty swallowing, 2 is limited, but the condition generally breathing functions. They may constipation, and gallstones can occur. runs a milder course. People with DM2 have cognitive impairment, In females, the muscles of the uterus may have a normal lifespan. While delayed speech, difficulty eating can behave abnormally, leading to mobility may be impaired at an early and drinking, and various other complications in pregnancy and labor. developmental delays. age, the ability to walk is often retained until around 60 years old. How is DM treated?

There currently is no cure or spe- Medications that increase cific treatment for DM. Treatment alertness may be used to treat is based on each person’s spe- Pacemakers and implant- excessive daytime sleepiness. cific signs and symptoms. able defibrillators can Laxatives, suppositories, or be used to treat abnor Physical therapy helps to restore enemas may be used to help and maintain muscle strength manage constipation. and function through exercise, as well as to maintain range of Gallbladder removal may motion through stretching. relieve persistent abdominal pain caused by gallstones. Routine physical activity may help control musculoskel- Testosterone replacement etal pain and maintain muscle therapy may be used to strength and endurance. treat infertility in males.

Educational and psycholog- ical interventions can help with learning disabilities. Over-the-counter pain remedies or prescription pain medications may Supportive aids such be used to reduce pain as braces, walkers, or in the skeletal muscles. wheelchairs may help those who experience problems with muscle weakness or fatigue.

Occupational therapy can help improve daily living and work skills.

Surgery can be used to re- move cataracts.

Assisted ventilation can help treat respiratory muscle weakness.

Cough assistance machines and assisted cough techniques can help people clear out se- cretions from the lungs.

Treatment with angiotensin con- verting enzyme (ACE) inhibitors and beta blockers may be used to help lessen stress on the heart. Please talk to your medical provider to obtain Heat and massage may more information on these treatments. help relieve muscle pain. MDA Glossary

Atrophy Muscular dystrophy A decrease in the size and mass A term that refers to a number of of muscle tissue diseases that cause progressive loss of muscle mass, resulting in weakness Cardiomyopathy and, sometimes, loss of mobility A condition in which the heart muscle is weakened, making it harder for the Mutation heart to pump blood to the body A flaw in the DNA code

Cerebral atrophy Myalgia Degeneration of the cerebrum Muscle pain

Conduction defect Myotonia Irregular electrical control The inability to relax muscles at will of the heartbeat Palpitation Dysphagia Missed heartbeat Difficulty swallowing Tachycardia Facial diplegia Fast heartbeat Paralysis of muscles in the face

Hypotonia Decreased muscle tone

To learn more about DM, visit mda.org or contact the MDA National Resource Center at 833-ASK-MDA1 (275-6321).

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66-0018 February 2019