What is Muscular Dystrophy?
To understand muscular dystrophy, it is first important to understand muscles. There are three different types of muscles in the body: smooth muscles, skeletal muscles, and cardiac muscles. Smooth muscles are found in the walls of some organs and blood vessels and are involuntary, meaning that a person can’t control the movements of these muscles. Skeletal muscles, also known as voluntary muscles, are attached to bones and are the primary muscles involved in movement and posture. Cardiac muscle is the muscle of the heart that is completely controlled by the brain.
Muscular dystrophy (MD) is referred to as a progressive deterioration of the skeletal muscles. There are several different types of MD, including myotonic, Duchenne, Becker, Limb-girdle, congenital, and Emery-Dreifuss. These subtypes of MD differ in severity, age at which onset of symptoms occurs, and prognosis. However, patients suffering from any type of MD will eventually need mobility support in the form of a wheelchair, as the muscles continue to degenerate.
MD is an inherited condition. The underlying cause of the disorder is a mutation of the genes responsible for the production of muscle proteins. A lack of production of these proteins as well as the productions of faulty muscle proteins inevitably leads to weakening of the muscles.
The mutated genes that are involved in MD are located on the x chromosome. As a rule, female have two x chromosomes, while males have one x chromosome and one y chromosome. Because MD is a recessive disease, females do not usually inherit the disease unless both x chromosomes are mutated. As a result, females are usually carriers of the disease, while males are likely to inherit the disease if they receive a mutated x chromosome from their mother. For males with a family history of MD, there is a 50% chance of inheriting the mutated x chromosome from the mother. In some cases, certain subtypes of MD, such as Myotonic MD, are dominant, meaning that inheriting just one of these genes will cause a person to develop the disease.