What is muscular dystrophy?
Muscular dystrophy, also referred to as MD, is a genetic disease that causes weakness and degeneration of the skeletal muscles, muscles that are used for voluntary movement. The weakness and degeneration are progressive, meaning that they become worse over time.
The disorder varies in the age of onset (when symptoms first begin), affected muscles, and in severity. All forms of muscular dystrophy grow worse as your affected muscles degenerate and weaken.
There are 30 different types of muscular dystrophy that are classified into nine categories. These categories are Becker, Congenital, Duchenne, Distal, Emery-Dreifuss, Facioscapulohumeral, Limb-Girdle, Myotonic, and Oculopharyngeal.
Symptoms of muscular dystrophy
The symptoms of muscular dystrophy vary depending on the type. In general, the symptoms involve progressive skeletal muscle deterioration as well as some effects on cardiac (heart) muscle.
Types of muscular dystrophy
The types of muscular dystrophy are:
Symptoms of this type of muscular dystrophy usually occur beginning in adolescence or early adulthood. They are similar to the symptoms of the Duchenne type but are not as severe. Becker muscular dystrophy progresses more slowly than Duchenne, and people with the Becker type typically live into middle age.
The symptoms of congenital muscular dystrophy begin at birth and include general muscle weakness and joint deformities. This type progresses slowly, but people living with it do experience a shortened lifespan.
Symptoms of Duchenne muscular dystrophy usually begin between two and six years of age and include general muscle weakness and wasting (gradual loss) that affects the pelvis, upper arms, and upper legs. Eventually, this type affects all voluntary muscles. People living with Duchenne muscular dystrophy typically do not live beyond their 20s.
The distal form of muscular dystrophy occurs later in life, usually beginning between 40 and 60 years of age. Symptoms include weakness and wasting of the hand, forearm, and lower leg muscles. This type progresses slowly and doesn’t normally leave you incapacitated.
Normally beginning during the teenage years, symptoms include weakness and wasting of the shoulder, upper arm, and shin muscles. It commonly causes joint deformities. While this type progresses slowly, people living with it may die suddenly from cardiac arrest (loss of heart function).
Beginning between childhood and early adulthood, symptoms of this type of muscular dystrophy include the weakening of facial muscles as well as shoulder and upper arm muscles. It progresses slowly with moments of rapid deterioration. Persons with this form of muscular dystrophy, however, can sometimes live for many decades after symptoms first appear.
Beginning during late childhood to middle age, persons with this type of muscular dystrophy first experience a weakening of muscles in the shoulder and hip. This type progresses slowly, and death is usually caused by cardiopulmonary (heart and lung) complications.
Normally beginning between the ages of 20 and 40, symptoms include weakness of all muscle groups and delayed relaxation of muscles. This type of muscular dystrophy progresses slowly, sometimes over 50 to 60 years.
Occurring later in life, usually between the ages of 40 and 70, this type affects eyelid and throat muscles first. It progresses slowly. People with this type of muscular dystrophy eventually have difficulty swallowing food and become emaciated.
Causes of muscular dystrophy
All types of muscular dystrophies are caused by mutations in your genes. You may or may not inherit these mutations from your parents.
Muscular dystrophy can be inherited in three ways:
Autosomal dominant inheritance
This happens when you receive a normal gene from one parent and a defective gene from your other parent. It can occur on any of your body’s 22 non-sex chromosomes. Both men and women are equally at risk, and the severity of the disorder varies from person to person.
Autosomal recessive inheritance
This occurs when both of your parents carry and pass on a faulty gene to you, but the faulty gene doesn’t affect either of your parents. Children in these families have a 25 percent chance of inheriting both copies of the defective gene and have a 50 percent chance of inheriting only one, making them a carrier and able to pass it along to their children. Both men and women have an equal chance of inheriting this type of muscular dystrophy.
X-linked recessive inheritance
This type of muscular dystrophy happens when a mother carries the affected gene on one of her two X chromosomes and passes it to her son, who has a 50 percent chance of inheriting the disorder. Daughters also have a 50 percent chance of inheriting this gene but aren’t usually affected because the healthy X chromosome they receive from their father offsets it.
Affected fathers can’t pass an X-linked disorder to their sons, but their daughters will carry it forward. Female carriers of this type usually exhibit milder symptoms of muscular dystrophy.
Diagnosis for muscular dystrophy
A doctor will review your medical history and your family history to see if there are any indications of muscle disease. They will also try to rule out any other reasons for muscle weakness, like prior surgeries, exposure to toxins, or medications you are currently taking.
In addition, your doctor will likely run a series of different tests and evaluations that can include:
Treatments for muscular dystrophy
There are no known cures for muscular dystrophy. Your doctor will recommend treatments to help you remain independent for as long as possible and to prevent any complications that might occur from muscle weakness, reduced mobility, and cardiac or respiratory difficulties.
Treatments can include a combination of physical therapy, medications, and surgery. They can help improve your quality of life and help you to live longer.
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Columbia University Department of Neurology: "“Types of Muscular Dystrophy and Neuromuscular Diseases."
Eunice Kennedy Shriver National Institute of Child Health and Human Development: "What are the types and symptoms of muscular dystrophy (MD)?"
National Institute of Neurological Disorders and Stroke: "Muscular Dystrophy: Hope Through Research."
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