PBL Problem 2013
Types of Muscular Dystrophies
Muscular dystrophies are a family of inherited (genetic) diseases that cause gradual wasting and weakening of muscles (and in some cases, of nerve tissue). In total, there are 9 types of generally accepted muscular dystrophies - each with its own characteristic age of onset, rate of progress etc - and the people affected by them are all characterized by muscle weakness, general difficulty in walking and sometimes deformities
The most common muscular dystrophy is Duchenne muscular dystrophy (DMD), followed by Becker muscular dystrophy (BMD). These two dystrophies feature the same kind of symptoms, and the diseases are inherited in the same way, although Duchenne MD is much more severe and debilitating. In fact, Becker MD is usually classified as a less severe form of Duchenne MD. They are both caused by a defect in the gene needed for the synthesis of a protein, called dystrophin, which is absolutely essential for the normal functioning of muscles. The result is that muscle fibers in affected patients are severely deficient in dystrophin (since the mutated version is not functional), which causes a decreased muscular function
Here's a list of the nine forms of muscular dystrophy:
Becker Muscular Dystrophy
Age of onset: 2 to 16 years
Symptoms: Similar to Duchenne MD, but less severe. They include general muscle weakness, especially in the upper leg and arms, and pelvic muscles. Calf muscles are generally hypertrophic (bigger than usual). Heart problems are also possible
Rate of Progression: Slower than Duchenne MD
Expected Lifespan: Well into middle age
Inheritance: X-linked recessive. BMD primarily affects young males, who inherit the disease through their mothers. Women can be carriers but usually exhibit no symptoms, because the dystrophin gene is located on the X chromosome - of which women have 2 copies - and one functioning copy of the dystrophin gene is generally sufficient for normal muscle function.
Muscular dystrophies are a family of inherited (genetic) diseases that cause gradual wasting and weakening of muscles (and in some cases, of nerve tissue). In total, there are 9 types of generally accepted muscular dystrophies - each with its own characteristic age of onset, rate of progress etc - and the people affected by them are all characterized by muscle weakness, general difficulty in walking and sometimes deformities
The most common muscular dystrophy is Duchenne muscular dystrophy (DMD), followed by Becker muscular dystrophy (BMD). These two dystrophies feature the same kind of symptoms, and the diseases are inherited in the same way, although Duchenne MD is much more severe and debilitating. In fact, Becker MD is usually classified as a less severe form of Duchenne MD. They are both caused by a defect in the gene needed for the synthesis of a protein, called dystrophin, which is absolutely essential for the normal functioning of muscles. The result is that muscle fibers in affected patients are severely deficient in dystrophin (since the mutated version is not functional), which causes a decreased muscular function
Here's a list of the nine forms of muscular dystrophy:
Becker Muscular Dystrophy
Age of onset: 2 to 16 years
Symptoms: Similar to Duchenne MD, but less severe. They include general muscle weakness, especially in the upper leg and arms, and pelvic muscles. Calf muscles are generally hypertrophic (bigger than usual). Heart problems are also possible
Rate of Progression: Slower than Duchenne MD
Expected Lifespan: Well into middle age
Inheritance: X-linked recessive. BMD primarily affects young males, who inherit the disease through their mothers. Women can be carriers but usually exhibit no symptoms, because the dystrophin gene is located on the X chromosome - of which women have 2 copies - and one functioning copy of the dystrophin gene is generally sufficient for normal muscle function.