The main sign of muscular dystrophy is progressive muscle weakness. Specific signs and symptoms begin at different ages and in different muscle groups, depending on the type of muscular dystrophy.

Duchenne type muscular dystrophy

This is the most common form of muscular dystrophy. Although girls can be carriers and mildly affected, it's much more common in boys.

About one-third of boys with Duchenne muscular dystrophy (DMD) don't have a family history of the disease, possibly because the gene involved may be subject to sudden abnormal change (spontaneous mutation).

Signs and symptoms typically appear in early childhood and may include:

• Frequent falls
• Difficulty rising from a lying or sitting up position
• Trouble running and jumping
• Waddling gait
• Walking on the toes
• Large calf muscles
• Muscle pain and stiffness
• Learning disabilities

Becker muscular dystrophy

Signs and symptoms are similar to those of Duchenne muscular dystrophy, but tend to be milder and progress more slowly. Symptoms generally begin in the teens but may not occur until the mid-20s or even later.

Other types of muscular dystrophy

Some types of muscular dystrophy are defined by a specific feature or by where in the body symptoms first begin. Examples include:

• Myotonic. Also known as Steinert's disease, this form is characterized by an inability to relax muscles at will following contractions. Myotonic muscular dystrophy is the most common form of adult-onset muscular dystrophy. Facial and neck muscles are usually the first to be affected.
• Facioscapulohumeral (FSHD). Muscle weakness typically begins in the face and shoulders. The shoulder blades might stick out like wings when a person with FSHD raises his or her arms. Onset usually occurs in the teenage years but may begin in childhood or as late as age 40.
• Congenital. This type affects boys and girls and is apparent at birth or before age 2. Some forms progress slowly and cause only mild disability, while others progress rapidly and cause severe impairment.
• Limb-girdle. Hip and shoulder muscles are usually the first affected. People with this type of muscular dystrophy may have difficulty lifting the front part of the foot and as a result may trip frequently. Onset usually begins in childhood or the teenage years.

Certain genes are involved in making proteins that protect muscle fibers from damage. Muscular dystrophy occurs when one of these genes is defective.

Each form of muscular dystrophy is caused by a genetic mutation particular to that type of the disease. Many of these mutations are inherited. But some occur spontaneously in the mother's egg or the developing embryo and can be passed on to the next generation.

Muscular dystrophy occurs in both sexes and in all ages and races. However, the most common variety, Duchenne, usually occurs in young boys. People with a family history of muscular dystrophy are at higher risk of developing the disease or passing it on to their children.

The complications of progressive muscle weakness include:

• Trouble walking. Some people with muscular dystrophy eventually need to use a wheelchair.
• Shortening of muscles or tendons around joints (contractures). Contractures can further limit mobility.
• Breathing problems. Progressive weakness can affect the muscles associated with breathing. People with muscular dystrophy may eventually need to use a breathing assistance device (ventilator), initially at night but possibly also during the day.
• Curved spine (scoliosis). Weakened muscles may be unable to hold the spine straight.
• Heart problems. Muscular dystrophy can reduce the efficiency of the heart muscle.
• Swallowing problems. If the muscles involved with swallowing are affected, nutritional problems and aspiration pneumonia may develop. Feeding tubes may be an option.