The Top Five Questions Asked

I am often asked questions about Spinal Bulbar Muscular Atrophy (better known as Kennedy's Disease). I would easily say that 90% of the questions asked could be summarized in the following Q&A.



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, while females who inherit the gene are usually just carriers.  Females, in some instances, may also exhibit symptoms (especially in their later years).

Q: How is Spinal Bulbar Muscular Atrophy (Kennedy's Disease) diagnosed?

A: Up until the mid-1990s, Kennedy's Disease was often misdiagnosed. Fortunately, there is a blood test today that checks a person's DNA for the defective chromosome. Any doctor or nurse can draw the blood and send it off to a DNA laboratory for testing. Test results are normally returned within three-to-six weeks. The test determines the number of CAG repeats within the Androgen Receptor (AR) gene.

• If you have less than34 repeats, that is considered normal
  
• If you have 34-39 repeats, you are considered "borderline" and you could experience some minor symptoms
  
• Repeats that are 40 or greater reflect that you have the full gene mutation (abnormal expansion of the CAG tandem repeat)
  

Since females have two X-chromosomes, they can have either one, and in rare cases both, chromosomes defective.

Q: Can the disease be passed on to my children?

A: If the mother is the only carrier of the defective gene (in the X-chromosome), there is a 50 % chance of passing the affected gene on to male children (in which case, they would develop symptoms in adulthood). The chance of passing the defective gene on to female children is also 50% (in which case, they would be carriers of the gene, but probably never develop the actual symptoms). If the father is the only carrier of the defective gene, the chances of passing the defective gene to a male child are 0%. However, it is 100 % certain that the gene will be passed on to a female child, and she will be a carrier of the gene. This Genetic Chart shows the possible ways the gene can be passed. 

Q: One of my parents has the defective gene. I have or am considering having children. Should I be tested or should I have my children tested?

A: Some families have even considered prenatal testing. If you have this concern, you should consult with a genetic counselor. These professionals are best equipped to help answer these type questions.

Q: Why don't we hear much about Kennedy's Disease?

A: Kennedy's Disease is considered a rare medical disorder. It is estimated that only 1 in 40,000 individuals worldwide have Kennedy's Disease. However, since many go misdiagnosed or undiagnosed for years, it is difficult to quantify how many have this gene defect. Normally, when a person is diagnosed with the defective gene, they usually comment that they have a brother, uncle, or grandfather that had similar symptoms.