by Kimberly Allen, RN
Kennedy disease is a member of the group of genetic diseases that are autosomal recessive known as spinal muscular atrophies. In the US the spinal muscular atrophies are second only to cystic fibrosis as the most commonly diagnosed autosomal recessive genetic diseases. Kennedy disease affects only boys as it is an X-linked genetic mutation affecting about 1 in 50,000 boys. It is most commonly found in people of Japanese descent but is also known to develop in Asian and Caucasians as well.
Kennedy disease is an autosomal recessive X-linked genetic disorder that is caused by a defect in the androgen receptor gene. Boys that inherit this disease have over 35 extra copies of CAG repeat section on the androgen receptor gene. Each cell in the human body has chromosomes that contain the genetic information for each person. All human chromosomes come in pairs that are numbered 1 through 22 plus the sex chromosomes which are labeled as X and Y. X-linked diseases are genetic disorders that are caused by a defective gene on the X chromosome. Because Kennedy disease is an autosomal recessive disorder girls which receive 2 X chromosomes do not develop the disease because the “good” chromosome is able to do the work that the other one can’t. However, boy have only 1 X chromosome and 1 Y chromosome therefore there is no extra “good” X chromosome to do the work of the defective one so they develop the disease. Girls though they do not develop the disease can be carriers and pass the defective gene on.
Kennedy disease is a slowly progressive disorder in which symptoms usually manifest between 20 to 40 years of age, however, they can develop as early as in the teens or as late as in the 70’s. The symptoms can vary from person to person however the most common symptom noticed first is uncontrollable muscle twitching. The twitching usually first noticed in your hands when they’re stretched out as well as muscle cramps with activity. Some also experience visible transient muscle twitches under their skin. As the disease progresses most people experience weakness tat starts in their pelvic and shoulder areas progressing down their limbs. Approximately half of men with Kennedy disease have unusually large calves and have difficulty walking and also have a tendency to fall. Climbing stairs becomes increasingly difficult as the disease progresses and around one third of men with the disease will need a wheel chair approximately 20 years after their disease first started. Later in the disease some also can develop weakness in the facial and tongue muscles which can cause difficulty swallowing and slurring speech as well as aspiration pneumonia. Some men also develop enlarged breasts and are either infertile or have a low sperm count while others develop type II diabetes.
It can take years for you to get the correct diagnosis because Kennedy disease is rare and the symptoms are very similar to other neuromuscular disorders like ALS or Lou Gehrig’s disease. However, there is a DNA blood test that can confirm whether or not you have Kennedy disease.
As with most genetic disorders there is no cure for Kennedy disease. However, because it is a slowly progressive disorder it does not affect life expectancy. Because the disease causes impaired muscle function and decreased mobility treatment is aimed at maintaining your optimal level of functioning and quality of life. Physical and occupational therapy as well as speech therapy are crucial components in treating Kennedy disease and helping you to maintain your optimal level of functioning for as long as possible.
The National Institute of Neurological Disorders and Stroke is currently researching various methods for the treatment of all motor neuron diseases including Kennedy disease. For information on clinical trials currently in progress throughout the US contact NIDS on line or ask your doctor for an NIH center near you.
Kimberly Allen is a registered nurse with an AND in nursing. She has worked in ACF, LCF and psychiatric facilities, although she spent most of her career as a home health expert. She is now a regular contributor to HealthAndFitnessTalk.com, dispensing advice and knowledge about medical issues and questions. You can reach her with any comments or questions at firstname.lastname@example.org.