According to the Mayo Clinic Muscular dystrophy (MD) is a group of inherited muscle diseases in which muscle fibers are unusually susceptible to damage. Muscles, primarily voluntary muscles, become progressively weaker. In the late stages of muscular dystrophy, fat and connective tissue often replace muscle fibers. Some types of muscular dystrophy affect heart muscles, other involuntary muscles and other organs.
The most common types of muscular dystrophy appear to be due to a genetic deficiency of the muscle protein dystrophin.
There's no cure for muscular dystrophy, but medications and therapy can slow the course of the disease.
Signs and symptoms vary according to the type of muscular dystrophy. In general, muscular dystrophy symptoms may include:
Apparent lack of coordination
Progressive crippling, resulting in fixations (contractures) of the muscles around your joints and loss of mobility
Specific signs and symptoms vary among the different forms of MD. Each type is different in the age of onset, which parts of the body the symptoms primarily affect and how rapidly the disease progresses.
These types of muscular dystrophies are due to a genetic defect of the protein dystrophin.
Duchenne's muscular dystrophy is the most severe form of dystrophinopathy. It occurs mostly in young boys and is the most common form of MD that affects children. Signs and symptoms of Duchenne's MD may include:
Large calf muscles
Difficulty getting up from a lying or sitting position
Weakness in lower leg muscles, resulting in difficulty running and jumping
Mild mental retardation, in some cases
Signs and symptoms of Duchenne's usually appear between the ages of 2 and 3. It first affects the muscles of the pelvis, upper arms and upper legs. By late childhood, most children with this form of muscular dystrophy are unable to walk. Most die by their 20s or early 30s, often from pneumonia, respiratory muscle weakness or cardiac complications.