Muscular Dystrophy - Causes

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Photo by: Yulia Podlesnova

All forms of muscular dystrophy are caused by wasting of muscle tissue. Muscle cells die, and muscles become weaker and unable to perform their normal functions. Researchers are still uncertain how this loss of muscle function takes place. They believe that cells may lose their ability to produce certain muscle proteins. Proteins are essential chemicals that occur in all cells and have many different functions. For example, they act as building blocks for cells and as enzymes. Enzymes are special kinds of proteins that control the rate at which chemical reactions take place in cells.

Researchers believe that some forms of MD occur because some muscle proteins are absent or present in smaller-than-average amounts. In such cases, muscle tissue becomes weak. Other muscle proteins may be needed to repair damage in muscle tissue. If those proteins are absent, muscles that are damaged cannot be repaired. In most cases, the connection between absent muscle proteins or reduced amounts of proteins and various forms of MD is simply not yet known.

What scientists do know is that MD is almost entirely a genetic disorder. A genetic disorder is a medical problem caused by defects in a person's genes. Genes are chemical units found within cells that carry essential information telling the cell what functions it should perform. Every person gets two sets of genes, one from each parent. Under most circumstances, the two sets of genes merge to produce a normal set of instructions. A cell follows those instructions to perform a normal set of functions.

Occasionally, a person inherits faulty genes from one or both of his or her parents. In such cases, the instructions provided to a cell can be incorrect and the cell is unable to perform its normal functions.

In the case of MD, a person may receive a single faulty gene from one parent or a pair of faulty genes, one from each parent. A single faulty gene may cause no problem at all. In that case, the person is said to be a carrier. A carrier can transmit the faulty gene to his or her own children. But it will not interfere with the person's own health.

In other cases, one faulty gene is all it takes to cause some form of MD. For example, DMD, FSH, OPMD, and some forms of LGMD and DD are thought to be caused by a single faulty gene. The faulty gene may make it impossible for muscle cells to function as they should. Muscle tissues weaken, and some form of muscular dystrophy results.

Other forms of MD require the presence of two faulty genes, one from each parent. CMD and some forms of LGMD and DD are thought to be caused by this mechanism. Again, the two faulty genes carry incorrect information to a cell and the cell does not function normally. It produces faulty muscle protein, an insufficient amount of the protein, or no protein at all. Muscle tissue weakens and dies, and MD results.