Muscular Dystrophy

What is muscular dystrophy?

Muscular dystrophy (MD) is a broad term that describes a genetic (inherited) disorder of the muscles. Muscular dystrophy causes the muscles in the body to become very weak. The muscles break down and are replaced with fatty deposits over time.

Other health problems commonly associated with muscular dystrophy include the following:

  • heart problems

  • scoliosis - a lateral, or sideways, curvature and rotation of the back bones (vertebrae), giving the appearance that the person is leaning to one side.

  • obesity

The most common forms of muscular dystrophy are Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy. The two forms are very similar, but Becker muscular dystrophy is less severe than DMD.  Girls are rarely affected by either of these two forms of muscular dystrophy.

What causes muscular dystrophy?

Duchenne muscular dystrophy is a genetic disease which means it is inherited. Our genes determine our traits, such as eye color and blood type. Genes are contained in the cells of our bodies on stick-like structures called chromosomes. There are normally 46 chromosomes in each cell of our body, or 23 pairs. The first 22 pairs are shared in common between males and females, while the last pair determine gender and are called the sex chromosome pair: females have two X chromosomes, while males have one X and one Y chromosome.

Duchenne muscular dystrophy is caused by an X-linked recessive gene. "X-linked" means that the gene causing the trait or the disorder is located on the X chromosome. Genes on the X chromosome can be recessive or dominant, and their expression in females and males is not the same because the genes on the Y chromosome do not exactly pair up with the genes on the X. X-linked recessive genes are expressed in females only if there are two copies of the gene (one on each X chromosome). However, for males there only needs to be one copy of an X-linked recessive gene in order for the trait or disorder to be expressed. For example, a woman can carry a recessive gene on one of the X chromosomes unknowingly, and pass it on to a son, who will express the trait or disease.

Therefore, half of the daughters have the gene and can pass it to the next generation. The other half do not have the gene and therefore cannot pass it on. Half of the sons do not have the gene and cannot pass it on. The other half of the sons have inherited the gene and will express the trait or disorder (in this case, DMD).

What are the symptoms of muscular dystrophy?

Muscular dystrophy is usually diagnosed in children between 3 and 6 years of age. Early signs of the illness include a delay in walking, difficulty rising from a sitting or lying position, and frequent falling, with weakness typically affecting the shoulder and pelvic muscle as one of the initial symptoms., with weakness typically affecting the shoulder and pelvic muscle as one of the initial symptoms. The following are the most common symptoms of muscular dystrophy. However, each child may experience symptoms differently. Symptoms may include:

  • clumsy movement

  • difficulty climbing stairs

  • frequently trips and falls

  • unable to jump or hop normally

  • tip toe walking

  • leg pain

  • facial weakness

  • inability to close eyes or whistle

  • shoulder and arm weakness

A tell-tale clinical characteristic for Duchenne muscular dystrophy (DMD) is Gowers' sign. Children with Duchenne muscular dystrophy find it very hard to get up from a sitting or lying position on the floor. They first pull up to their hands and knees. The child walks his/her hands up their legs to brace themselves as they rise to a standing position.

Another classic symptom of muscular dystrophy is known as the "slip through" symptom. Your child's physician puts his/her hands around the sides of the child's chest, right up under the arms. As the child is lifted up, the shoulders weaken and move upward, almost allowing the child to slip through your child's physician's hands.

In addition, children with muscular dystrophy often have very large calf muscles due to the large amounts of fatty deposits that are replacing muscle.