Duchenne muscular dystrophy (DMD): This common neuromuscular disorder affects males almost exclusively, but some females show mild characteristics of the disorder. With DMD, an abnormal gene on the X chromosome prevents the production of an important muscle protein called dystrophin. Eventually, muscle cells break down, resulting in muscle weakness and lost mobility.
Becker muscular dystrophy (BMD): BMD is similar to DMD, but with this disorder the abnormal gene does make some dystrophin. However, it either makes an abnormal form of dystrophin or not enough of it. As a result, some males with this form appear less affected than males with Duchenne muscular dystrophy.
Facioscapulohumeral muscular dystrophy: This disorder mainly affects the face, shoulders and upper arms. Muscle weakness results from a defect on chromosome 4, found throughout the body. Over time, other muscles and body parts can show slow—but progressive—weakening.
Congenital muscular dystrophy (CMD): This group of disorders leads to severe muscle weakness noticeable from birth. CMD affects both males and females. Most forms affect bone development, heart and lung function, brain function and mobility. Types of CMD include:
- Bethlem myopathy.
- Muscle-eye-brain disease.
- Walker-Warburg syndrome.
- CMD with rigid spine syndrome.
Myotonic muscular dystrophy: This type affects all or most muscles and some organs. The term “myotonic” refers to an inability to relax a muscle normally.