Doctors' Views

Parkinson's Disease Gene Characteristics Identified

BETHESDA--Parkinson's disease is a degenerative disease of the inner brain. It is the second most common degenerative brain disease after Alzheimer's disease. It is not rare and affects 1 percent of the U.S. population over the age of 50 years.

James Parkinson first described the features of the illness in 1817. Patients with the disease, now named after him, typically have a "pill-rolling" tremor while resting (when the extremity is not in use), rigid muscles, slowed body movements, and unstable body positioning. Patients often also have dementia.

The cause of Parkinson's disease is not known. For many years, there have been a variety of theories posed as to the roles of heredity (influence of one's genes and genetic background) as opposed to environmental factors. The environmental theories were supported by the wave of Parkinson's disease that affected many persons who suffered from the influenza pandemic of 1918.

Genes are the elemental structures (like tiny computers) within the nucleus of every cell of animals. Genes are preprogrammed to express the development of the body's physical structure, as well as the development of the immune systems and much of the emotional character. Genes of an individual are inherited from each of one's parents.

Genes also are coded to program the ability of specialized cells of the body to send out various chemical messengers. An example of such specialized cells are the cells of the various compartments of the brain that transmit brain messages.

Parkinson's disease is believed to result, in part, from a deficiency of the chemical neurotransmitter called dopamine in an area of the brain referred to as the substantia nigra.

In a recent study published in the journal SCIENCE [274(5290):1197], Dr. Mihael H. Polymeropoulos and associates at the National Institutes of Health described the actual design of a part of the gene on a chromosome that is believed to play a role in expressing an inherited form of Parkinson's disease.

This extremely important finding will facilitate the final identification of the entire Parkinson's disease gene and lead to a final understanding of the cause of the disease. Newer and more accurate and safe treatment methods will result.

To date treatment methods have included medications, such as amantadine (SYMADINE, SYMMETREL), and other medications to decrease the nerve functioning causing the tremor and rigidity in the early stages of disease. Later in the illness, levodopa/carbidopa (SINEMET) is used. Newer medications, such as selegiline (ELDEPRYL) can reduce SINEMET requirements (SINEMET has frequent side effects).

Currently being studied for the evaluation of Parkinson's disease patients are newer, more accurate imaging methods to see the brain (SPECT imaging). Transplants of cells from fetuses that can produce the dopamine chemical transmitter are being evaluated in patients with Parkinson's disease. Dopamine injections directly into the brain is also being looked into. In the future, more brain surgery techniques are likely to be studied. For patients, families, and friends who are affected by this disabling disease, it is some gratification to know such research is ongoing.

Last Editorial Review: 7/8/2004