Today and Sunday’s posts address many questions asked about Kennedy’s Disease. This information is also part the “welcome packet” that is sent out to those who join the Kennedy’s Disease Association.
Q: What is Kennedy’s Disease?
A: Kennedy's Disease (also known as Spinal Bulbar Muscular Atrophy, SBMA, or Kennedy's Syndrome) is a rare and currently incurable and non-treatable X-linked recessive genetic progressive neuro-muscular disease. Both the spinal and bulbar neurons are affected causing muscle weakness and wasting (atrophy) throughout the body which is most noticeable in the extremities (legs/arms), it is also especially noticeable in the face and throat, and causes speech and swallowing difficulties, along with major muscle cramps as well as other symptoms.
Q: What are some of the symptoms of Kennedy’s Disease?
A: See the following link: KD Symptoms
Q: When do you first start seeing signs of the disease?
A: Generally, symptoms begin to appear in the late 20’s or early 30’s. However, there have been cases where the symptoms showed up as early as the late teens or not until the 60’s.
Q: Who gets Kennedy’s Disease?
A: Kennedy's Disease is a genetic disease, passed on from generation to generation in a family. It is an X-linked recessive inherited gene. Generally males who inherit the gene exhibit symptoms. Females, who inherit the gene, are carriers and may also exhibit symptoms, usually later in life.
Q: Is there a treatment or cure for Kennedy’s Disease?
A: Currently there is no treatment or cure. Recent research, however, show some promising signs. Read about research that is taking place at this link: Research. (Note: You can also search this blog for the most current reports on research)
Q. What causes the muscle cells to die?
A. The direct cause of the muscle cell death is believed to be the death of the nerve cells that control the contraction of the muscle cells. These nerve cells are known as motor neurons. Motor neurons are the cells that connect the brain to the muscle cells. When you wish to contract a muscle to pick up a pencil, for example, your brain sends signals to the motor neurons that control those muscles. The motor neurons then convey the signal to the muscle cells and the muscle cells contract, performing the movement that you envisioned in your brain.
In KD, the motor neurons die and so the connection from the brain to the muscle cells is broken. As a direct result of the loss of the motor neuron, the muscle cells die as well. Whenever muscle cells lose their motor neuron, they will usually die. It is generally thought that KD does not directly cause the muscle cells to die although there is some recent evidence that KD may result in some changes in the muscle.
Q. What causes the motor neurons to die?
A: This is the million dollar question. The straight answer is that we really do not know for sure. There is a lot of evidence that the motor neuron cell death may be due to the inability of the cell from KD patients to adequately recycle proteins and this results in the build up of old, trashy proteins. This build up of trash is believed to somehow be toxic to the cell. (Note: See Dr. Taylor’s research article in this blog for the most current assessment of what happens)
Q. Why can’t the cell recycle proteins?
A: KD is a genetic disease – this means that KD patients have a defective gene. The function of genes is to tell the cell how to make a specific protein and a cell can only make proteins for which there is a gene. For example, we all have a gene to tell our cells how to make hemoglobin, the protein that carries oxygen in our blood. Without that gene, our cells would not be able to make any hemoglobin. Since we need hemoglobin to live, such an individual would never even be born. However, occasionally, a gene for a specific protein may be changed so that the cells would make an altered form of the protein. This altered protein may still work, but possibly not as well. This is what happens in sickle cell anemia. The hemoglobin gene has been altered and the hemoglobin made does not work as well.
Since KD is a genetic disease, patients with KD must have an altered gene. The gene that is altered is the one that tells the cells how to make the protein known as the androgen receptor (AR). The normal function of the AR is to mediate the actions of testosterone. Without the AR, testosterone would have no effect on a cell. In men with KD, the AR that is made is altered. It still works but sometimes not as well. The current thinking is that the problem with those with KD, however, is that the altered AR cannot be removed by the cell.
Typically, once used, the AR is destroyed by the cell. This is done by processes that help remove all proteins. Even worse, when the cell tries to remove the AR, the altered form of AR jams up these cellular processes preventing the cells from removing any proteins. Apparently, the nerve cell must be able to remove proteins to survive, so the overall effect of the jamming is to kill the cells. Much of the research on KD right now involves investigating ways to ‘un-jam’ these protein removal mechanisms and prevent the death of the cell.