Duchenne muscular dystrophy is the most common fatal genetic disorder diagnosed in childhood, affecting approximately 1 in every 5,000 school-aged males. It is caused by mutations in the dystrophin gene. Because the dystrophin gene is located on the X chromosome, Duchenne muscular dystrophy primarily affects boys. Girls and women can be carriers of a dystrophin mutation and pass it on to their sons, but it is rare for them to experience symptoms themselves. Duchenne muscular dystrophy occurs in all races and ethnicities. It may be slightly more common in Hispanic populations and slightly less common in African-American populations. Duchenne causes progressive loss of muscle strength that starts in early childhood and typically results in using a wheelchair by the teenage years. It also cases serious medical problems relating to the heart and lungs. Young men with Duchenne typically live into their late twenties to thirties. There is currently no cure for Duchenne muscular dystrophy. There are several treatments currently approved by the FDA to slow down progression of the disease, including corticosteroids and several targeted therapies that must be matched to the specific mutation a person has.

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Becker muscular dystrophy is related to Duchenne muscular dystrophy (see above) because both disorders are caused by mutations in the dystrophin gene. It is about three times less common than Duchenne muscular dystrophy. People with Becker muscular dystrophy have muscle weakness that typically starts later and progresses more slowly than people with Duchenne. Men with Becker typically live into their mid-forties. There is no cure for Becker muscular dystrophy, but corticosteroids are currently approved by the FDA to slow down progression of the disease. Clinical trials for targeted therapies are ongoing in the United States.

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Myotonic dystrophy is a complex genetic condition that affects various muscle groups in the body. There are two types of myotonic dystrophy: type 1 (also called Steinert disease), and type 2, each caused by a different change in a single gene. Both types can affect males and females. Common symptoms in both types of myotonic dystrophy include muscle weakness and delayed muscle relaxation after contraction, known as myotonia. Treatment focuses on symptom management, including medications, adaptive equipment, and physical/occupational therapy.

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Congenital muscular dystrophies are a group of genetic conditions which are characterized by muscle weakness in infancy. An infant is diagnosed with a congenital muscular dystrophy based upon:

• the findings of a clinical evaluation
• identification of characteristic symptoms of one of the conditions, such as decreased muscle tone/muscle weakness, delay or early stopping of gross motor development with joint/spinal rigidity
• an evaluation of medical and family history
• specialized tests, such as muscle biopsy and molecular genetic testing

Depending upon the type of congenital muscular dystrophy, a person may also have cardiac, respiratory, or central nervous system challenges as they age. Currently there is no cure for any type of congenital muscular dystrophies. Treatment focuses on symptom management, including medications, surgery, and physical/occupational therapy.

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Distal muscular dystrophy is a group of muscular dystrophies which begin with distal muscle weakness. The distal muscle are the muscles in the lower arms, lower legs, hands, and feet. Over time muscle weakness occurs in non-distal muscles. However, distal muscular dystrophy is typically not considered life-threatening and does not impact an individual's learning ability. Many people with distal muscular dystrophy are diagnosed in adulthood. Distal muscular dystrophy affects both men and women, can occur at any age, and the symptoms, and severity vary. Treatment is symptom specific.

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Emery-Dreifuss muscular dystrophy (EDMD) is a rare MD that is due to a change in one of three genes. Which gene is changed determines how EDMD is passed on from generation to generation, if both males and females are affected, or if only males are affected. EDMD affects the muscles of the heart and skeleton. Individuals with this condition have heart problems and difficulty with movement. Typically, symptoms of EDMD appear during childhood and the first symptom is frequently deformities of the joints. These deformities are called contractures and often impact the elbows, ankles, and neck. The age of onset of symptoms and their progression and severity varies among families and among family members. Treatment is focused on symptom management and can include physical therapy and surgery.

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Limb girdle muscular dystrophy is a group of muscular dystrophies which involve muscle weakness and wasting of muscles in the arms and legs. The muscles of the shoulders, upper arms, pelvic area, and thighs are most impacted. Some forms of limb girdle muscular dystrophy may also involve weakness of the heart muscle and muscles involved with breathing. Limb girdle muscular dystrophy affects both men and women, can occur at any age, and the symptoms and severity vary. Mutations in any of several dozen genes can cause limb girdle muscular dystrophy. Treatment is symptom specific.

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Oculopharyngeal muscular dystrophy (OPMD) is a muscle condition that affects both males and females with the first symptoms typically occurring when an individual is between age 40 and 60. The most common symptoms are droopy eyelids and difficulty swallowing. As the condition progresses, individuals typically develop weakness of the muscles in their tongue and limbs, which causes difficulty with eating and limited ability to perform physical activities such as climbing stairs. Treatment options are symptom specific. Research to understand the full clinical spectrum of oculopharyngeal muscular dystrophy is ongoing.

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