There are nine major types of MD affecting people of all ages, from infancy to middle age or later. The two most common types of MD affect children:

Duchenne muscular dystrophy (DMD)
Becker muscular dystrophy (BMD)

Both DMD and BMD affect boys almost exclusively, but in rare cases can also affect girls. Both Duchenne and Becker muscular dystrophy cause weak muscles, lack of coordination and progressive disability.

Duchenne muscular dystrophy (DMD), the most common type of the disease, is caused by a problem with the gene that makes a protein called dystrophin. This protein helps muscle cells keep their shape and strength. Without it, muscles break down and a person gradually becomes weaker. DMD begins with muscle loss in the pelvis, upper arms and legs. DMD affects boys. They may have:

	Difficulty walking, such as being late in learning how to walk (more than 18 months old), having a waddling gait or walking on toes or balls of the feet.
	Difficulty running or jumping caused by weakness in leg muscles.
	Frequent falls, stumbling and difficulty climbing stairs.
	Difficulty standing from a lying or sitting position.
	Reduced endurance.
	Enlarged calf muscles.
	Enlarged calf muscles.

Symptoms usually start between ages 2 and 6. By age 10 or 12, kids with DMD often need to use a wheelchair. The heart may also be affected, and people with DMD need to be followed closely by a lung and heart specialist. They can also develop scoliosis (curvature of the spine) and tightness in their joints. Over time, even the muscles that control breathing get weaker, and a person might need a ventilator to breathe. People with DMD usually do not survive beyond their late teens or early adulthood.

Becker muscular dystrophy (BMD), begins with muscle loss in the hips, pelvis, thighs and shoulders. Becker is basically a milder form of Duchenne and like DMD, affects boys. Children with BMD may have:

	Difficulties similar to DMD.
	A waddling gait, perhaps walking on toes or sticking out the abdomen to balance weak muscles.

The disease is very similar to DMD, but its symptoms may start later and can be less severe. With BMD, symptoms like muscle breakdown and weakness sometimes don't begin until age 10 or even in adulthood. People with BMD can also have breathing, heart, bone, muscle, and joint problems. Many people with BMD can live long, active lives without using a wheelchair. How long a person with BMD can live varies depending on the severity of any breathing and heart problems.

OTHER TYPES OF MUSCULAR DYSTROPHY:

The life expectancy for many of these forms of muscular dystrophy depends on the degree to which a person's muscles are weakened as well as how much the heart and lungs are affected.

	Emery-Dreifuss muscular dystrophy (EDMD) typically starts causing symptoms in late childhood to early teens and sometimes as late as age 25. EDMD is another form of muscular dystrophy that affects mostly boys. It involves muscles in the shoulders, upper arms, and shins, and it often causes joint problems (joints can become tighter in people with EDMD). The heart muscle may also be affected.
	Limb-girdle muscular dystrophy (LGMD) affects boys and girls equally, weakening muscles in the shoulders and upper arms and around the hips and thighs. LGMD can begin as early as childhood or as late as mid-adulthood, and it often progresses slowly. Over time, a wheelchair might be necessary to get around. There are many different types of LGMD, each with its own specific features.
	Facioscapulohumeral muscular dystrophy (FSHD) can affect both guys and girls, and it usually begins during the teens or early adulthood. FSHD affects muscles in the face and shoulders and sometimes causes weakness in the lower legs. People with this type of MD might have trouble raising their arms, whistling, or tightly closing their eyes. How much a person with this form of muscular dystrophy is affected by the condition varies from person to person. It can be quite mild in some people.
	Myotonic dystrophy (MMD) is a form of muscular dystrophy in which the muscles have difficulty relaxing. In teens, it can cause a number of problems, including muscle weakness and wasting (where the muscles shrink over time), cataracts, and heart problems.
	Congenital muscular dystrophy (CMD) is the term for all types of MD that show signs in babies and young children, although the MD isn't always diagnosed right away. Like other forms of MD, CMD involves muscle weakness and poor muscle tone. Occurring in both girls and boys, it can have different symptoms. It varies in how severely it affects people and how quickly or slowly it worsens. In rare cases, CMD can cause learning disabilities or mental retardation.