Causes and Risk Factors of Muscular Dystrophy

If you have muscular dystrophy or suspect you have it, you need to check in with your doctor. Properly treating and understanding your condition is paramount to successful management of the condition. And one important component of understanding the disease is knowing what causes muscular dystrophy.

Knowing this information can help identify anything that can be done to minimize your risk of getting it.

Types and Genetics

There are nine different types and manifestations of muscular dystrophy. Since it is a genetic disease, the type you have depends on which mutation has taken place on a specific gene. Other factors may also play a role, and each type may carry with it a different prognosis and treatment course.

The types of muscular dystrophy include:

• Myotonic (also known as Steinert's disease)
• Duchenne muscular dystrophy
• Becker
• Limb-girdle
• Congenital
• Oculopharyngeal
• Facioscapulohumeral
• Distal
• Emery-Dreifuss

Common Causes

To understand the cause of muscular dystrophy, you need to understand how the disease affects your muscles. As stated, the condition is marked by progressive weakness and wasting of muscle cells. But what causes this muscle wasting?

What Is Dystrophin?

Your muscles are made up of bundles of muscle fibers. These fibers are covered in a sheath, and surrounding the sheath are various structures like nerves and proteins.

These help the muscle fiber—and your muscles—contract properly.

Dystrophin is one such protein surrounding your muscle fibers. First identified in 1986, it is known to provide a link between the outer portion of the muscle and the extracellular matrix where the muscle fiber resides. The role of the protein is to provide a scaffold and structural framework for your muscle fibers to work properly.

Dystrophin transfers the force of a muscle contraction from the inside of your muscle fiber to the outside, leading to a forcible muscle contraction. The absence of dystrophin leads to Duchenne muscular dystrophy while production of faulty dystrophin leads to Becker's muscular dystrophy.

Other abnormal genetic components and proteins are thought to cause the other forms of muscular dystrophy.  

Genetics

So how does genetics affect your chances and the causes of acquiring muscular dystrophy? For starters, the genetic anomaly that causes muscular dystrophy lies on the X chromosome. (Remember, you get one chromosome from each parent; an X chromosome comes from your mother. If an X chromosome comes from your father, you will be female; a Y chromosome from your dad makes you male.)

Men who have the muscular dystrophy gene on their X chromosome will have the disease. They will then pass that gene onto any female offspring. They cannot pass the gene to a male child, as fathers give their male children a Y chromosome. Women may have the gene on one X chromosome and be carrying the disease without presenting with it. If both X chromosomes in a woman are carrying the defective gene, she has a chance of exhibiting symptoms of muscular dystrophy.

With this logic, a woman has a 50 percent chance of passing their X chromosome onto a male or female child.

Occasionally muscular dystrophy occurs even when there is no family history of the disease. This may occur for one of two reasons, including:

• The mutation has simply been latent for generations on the mother's X chromosome.
• The mutation occurred as a new problem in the mother's egg cells.

Keep in mind that there is little you can personally do to affect any genetic mutation on your chromosomes. When a mutation occurs, there is a chance that you will show some characteristics of the disease.

Lifestyle Risk Factors

Since there is a genetic factor for acquiring muscular dystrophy, there is no lifestyle change that you can make to decrease your likelihood of getting it. If the genetic makeup is there and active in specific chromosomes in your body, you may get muscular dystrophy.

However, researchers have identified risk factors for complications and early death if you already have muscular dystrophy. In a 2017 study published in the Journal of the American Heart Association, researchers identified three common risk factors that were present in people with Duchenne muscular dystrophy who experienced poor outcomes including early death. These included:

• Being underweight as measured by body mass index
• Having poor lung function
• Having a high blood concentration of a protein linked to  cardiac damage

People with Duchenne muscular dystrophy may have an improved outcome and longer life if their cardiac function, lung function, and weight are appropriately maintained. This can be done with the help of your doctor and medical team.

Understanding the cause of muscular dystrophy can help put your mind at ease. It is a hereditary disease determined by genetics. This leaves little you can do to prevent it from occurring, but if you have muscular dystrophy, you should work closely with your doctor and medical team to maximize your overall function and outcome.

Source:

Cheeran, D., et al. Predictors of Death in Adults With Duchenne Muscular Dystrophy–Associated Cardiomyopathy. Journal of the American Heart Association, 2017; 6 (10): e006340 DOI: 10.1161/JAHA.117.006340