A Guide for Patients and Families

What is... Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) Because the DMD gene is located on the is the most common form of muscular X-chromosome, it primarily affects males, dystrophy. It is a genetic disorder while females typically are carriers. characterized by progressive weakness However, some females can experience and degeneration of the skeletal muscles varying degrees of physical Duchenne that control movement. symptoms and are therefore called manifesting carriers. Duchenne affects approximately 1 in 5,000 live male births. It is estimated that about DMD typically is inherited through the 20,000 children are diagnosed with mother; however, in about 25% of cases, Duchenne globally each year. the disease occurs spontaneously in people who do not have a family history of DMD. DMD is classified as a dystrophinopathy, a muscle disease that results from the There is no cure for DMD, but medications deficiency of a protein called dystrophin. and therapy can help manage some symptoms and potentially slow the course In Duchenne, a mutation in the DMD of the disease. gene interferes with the production of the dystrophin protein, which is needed to form and maintain healthy muscle. Lack of the dystrophin protein in muscle cells causes them to be fragile and easily damaged. What are the signs and symptoms of DMD? How is DMD treated? DMD is a multi-systemic condition affecting many parts of the body and resulting in atrophy of the skeletal, cardiac (heart), and pulmonary (lung) muscles.

Physical therapy through exercise Emflaza* is the only corticosteroid helps to restore and maintain mus- that has been approved by the cle strength and function. Stretching US Food and Drug Administration Nervous system Skeleton and muscle helps to maintain range of motion. for the treatment of Duchenne in • Developmental delay • Muscle weakness individuals 5 years of age and older. • Motor delay • Fatigue Braces, also called orthoses, • Muscle cramps support the ankle and foot or may Cognition • Difficulty walking extend up over the knee. Ankle-foot Corticosteroids (such as • Learning disability • Difficulty climbing stairs orthoses (AFOs) are sometimes prednisone) are commonly • Gait abnormalities prescribed for night wear to keep used in DMD to help Gastrointestinal • Contractures the foot from pointing downward preserve muscle strength • Dysphagia • Pseudohypertrophy and keep the Achilles tendon and function, to prevent • Constipation • Lordosis stretched while a child is sleeping. scoliosis, and to prolong the • Reflux • Scoliosis time that people with DMD • Gastroparesis Occupational therapy can help can walk. It’s thought that Lungs improve daily living and work skills. steroids work, at least in part, Heart • Breathing difficulties by reducing inflammation. • Cardiomyopathy • Respiratory infections Assisted ventilation can help treat However, corticosteroids also • Sleep apnea respiratory muscle weakness. cause unwanted side effects such as increased appetite, weight gain, loss of bone mass, and cataracts. Educational and psycholog- ical interventions can help Corrective orthopedic What should I know about DMD? with learning disabilities. surgery, including spine- straightening surgery, may help make sitting, sleeping, 1 4 8 DMD symptom onset occurs in A small percentage of boys with Heart and respiratory muscle and breathing more early childhood, usually between DMD have some degree of learning problems begin in the teen years comfortable. the ages of 3 and 5 years. disability, including problems in and can lead to serious three general areas: attention complications. focusing, verbal learning and 2 Early signs of Duchenne may memory, and emotional interaction. Treatment with angiotensin include delayed ability to sit, stand, 9 Weakened respiratory muscles or walk, and difficulties learning to make it difficult to cough, leading to converting enzyme (ACE) inhibitors speak. Muscle weakness usually 5 Muscle weakness worsens with age increased risk of serious respiratory and beta blockers may be used to begins in the hips, pelvic area, and progresses to the arms, legs, infection. A simple cold can quickly slow the course of cardiac muscle upper legs, and shoulders. The and trunk. progress to pneumonia. deterioration in DMD. calves may be enlarged.

6 While disease progression varies, 10 Thanks to advances in cardiac and Exondys 51* is an “exon skipping” 3 Children with DMD typically develop boys, on average, lose their ability respiratory care, life expectancy for drug that targets a section of DNA an unusual walk and difficulty to walk, and transition to fulltime individuals with DMD is increasing called exon 51. It is approved by running and climbing stairs. Some wheelchair use at age 12. and many young adults with DMD the FDA for treatment of individuals will have problems getting up from attend college, have careers, get the floor and may use a distinctive married, and have children. who have a confirmed mutation of method known as Gower’s 7 Beginning at about 10 years of age, the DMD gene that is amenable to a maneuver or Gower’s sign to “walk” the diaphragm and other muscles therapeutic strategy called exon 51 their hands up their thighs in order that operate the lungs may weaken, 11 Survival into the early 30s is skipping and may help up to 13% of to stand up. DMD may also affect making the lungs less effective at becoming more common, and there individuals with DMD. Exondys 51 is learning and memory, as well as moving air in and out. Signs of poor are cases of men with DMD living not a cure for DMD, but it potentially communication and certain respiratory function can include into their 40s and 50s. emotional skills. headaches, difficulty concentrating could lessen the severe muscle or staying awake, and nightmares. weakness and atrophy that is the hallmark of the disease. *Please talk to your medical provider to obtain more information on these treatments. MDA Glossary

Atrophy Gower’s maneuver A decrease in the size and mass of A person’s use of their hands and muscle tissue arms to “walk” up their own body in order to rise from a squatting position; Cardiomyopathy this medical sign indicates weakness A condition in which the heart muscle is of the muscles in the hips and legs weakened, making it harder for the heart to pump blood to the body Lordosis Posture characterized by an inward Contracture curving of the lower back A shortening of muscles or tendons around joints that can limit mobility Muscular dystrophy A term that refers to a number of Corticosteroids diseases that cause progressive loss A group of steroid hormones that have of muscle mass, resulting in weakness been shown to dampen the inflammatory and, sometimes, loss of mobility response in damaged muscle Mutation Dysphagia A flaw in the DNA code Difficulty swallowing Pseudohypertrophy Exon skipping A condition in which muscles A treatment strategy in which sections become enlarged with deposits of of genetic code are “skipped,” allowing wfat and fibrous tissue cells to manufacture partially functional dystrophin, the muscle protein missing Scoliosis in DMD An abnormal sideways curvature in the spine that occurs when Gastroparesis weakened muscles are unable to Also known as delayed gastric emptying; hold the spine straight a condition that affects the ability of the stomach to empty its contents into the small intestine, even though there is no blockage

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

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66-0017 February 2019