by Darian Peters

Created on: February 14, 2011

Kennedy’s disease is a genetic disease of human beings that involves neuromuscular problems. It is caused by a mutation of NR3C4, the androgen receptor. The disease has similarities to androgen insensitivity syndrome and other several other diseases, such as Huntington’s disease. There are many potential symptoms of the disease that can appear as it progresses including problems with the endocrine system, neurological problems, and muscular problems. There is still much to be done to provide effective treatments and cure this little-known disease.

The underlying cause of Kennedy’s disease, also known as Spinal Bulbar Muscular Atrophy, is a genetic one. In particular, it is a sex-linked mutation, appearing on the X chromosome. Males have one X and one Y chromosome and will express the symptoms of such diseases fully. Females, who have two X chromosomes and no Y chromosome, will only show milder symptoms of the disease. They may even be asymptomatic.

The specific problem that this mutation on the X chromosome causes is with the androgen receptor. Also called NR3C4, this is a nuclear receptor, which are proteins that sense hormones such as thyroid and steroid. They androgen receptor can be activated by the two hormones testosterone and dihydrotestosterone. The specific nature of the mutation involved is CAG repeat expansion in the first exon of the gene for the androgen receptor.

The disease leads to a body that can’t cope with testosterone and this will eventually cause damage to the motor neurons and a wasting away muscles. As it progresses the disease can lead to endocrine problems such as reduced fertility and low sperm count. It can also cause problems such as weakness and a loss of muscle mass. There can also be signs such as hand tremor, cramps, and fatigue. However, the condition does progress very slowly and the symptoms probably won’t be noticeable until middle age, probably leading to the person retiring. Pneumonia becomes a threat as it becomes more difficult to clear phlegm from the lungs.

Kennedy’s disease is, thankfully, very rare. But this means that, as with other rare conditions, woefully little research has been done and money is hard to come by. Especially in a climate where medical research funding is being squeezed. This means that the effective treatment and curing of the disease are still not there yet. The search for better treatments and, ultimately, for a cure are still ongoing and will be for the foreseeable future.

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