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Kennedy disease

Kennedy disease (KD) or X-linked spinal-bulbar muscle atrophy is a neuromuscular disease associated with mutations of the androgen receptor (AR). Because of its endocrine manifestations related to the impairment of the AR, it can be viewed as a variation of the disorders of the androgen insensitivity syndrome (AIS). It is named after WR Kennedy, a neurologist who was among the first to describe this disease. more...

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As a sex-linked disease, KD affects males, while females are carriers. The gene for the AR is located on the X chromosome (Xq11-q12).


The distinctive AR mutation of Kennedy disease, reported in 1991, involves multiplied CAG repeats in the first exon (trinucleotide repeats). Such a CAG repeat encodes a polyglutamine tract in a part of the androgen receptor outside of the binding sites. The more CAG repeats are present, the more severe the disease. The mechanism by which this type of mutation causes neuromuscular disease is not completely understood, specifically as complete AIS does not affect neuromuscular activity. KD may share mechanistic features with other neurodegenerative disorders that are caused by polyglutamine expansion, such as Huntington's disease.

Signs and symptoms

Ages of onset and severity of manifestations in affected males vary from adolescence to old age, but most commonly develop in middle adult life. The latest onset was described in a male of 84 years of age. KD does not usually compromise longevity. The syndrome has neuromuscular and endocrine manifestations:


Early signs often include weakness of tongue and mouth muscles, fasciculations, and gradually increasing weakness of proximal limb muscles with muscle wasting. In some cases, premature muscle fatigue begins in adolescence. Neuromuscular management is supportive, and the disease progresses very slowly and often does not lead to extreme disability.


Endocrine manifestations of this disorder are variable and rarely include underdevelopment of internal or external genitalia. In other words, most people affected with Kennedy disease are relatively normal XY men with normal fertility. However, exaggerated and persistent gynecomastia is common and often the only symptom, while in more severe forms testicular atrophy and infertility have been described. Many affected men have the mildly high LH, testosterone, and estradiol levels characteristic of other forms of the androgen insensitivity syndrome.

Homozygous females

Homozygous females, whose both X chromosomes have a mutation leading to CAG expansion of the AR gene, show only mild symptoms of muscle cramps and twitching. No endocrinopathy has been described.


This disorder was described by Kennedy in 1968. In 1991 it was recognized that the AR is involved in the disease process. The disease is probably more common than originally thought. A study in Scandinavia suggested a prevalence of 1.3/8,500 making KD the most common form of motor neuron disease in the specific area studied; nobody had been diagnosed before 1995. It has been suggested that some men with KS are may be misdiagnosed to have amyotrophic lateral sclerosis (ALS, also Lou Gehrig's disease).


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Ask about bladder, bowel pain with vulvar disease
From OB/GYN News, 1/1/05 by Mary Ann Moon

WASHINGTON -- Women who have vulvar disease should be asked specifically about bladder and bowel pain, and these symptoms also must be addressed, Colleen M. Kennedy, M.D., of the University of Iowa, Iowa City, advised.

Women with vulvar disease are twice as likely as are general gynecology patients to have bladder pain and bowel pain. "We hypothesize that certain vulvar or vaginal diseases are not isolated clinical entities, but rather represent symptoms of a global or generalized pelvic floor disorder--a pelvic floor pain disorder," she said at the annual meeting of the Central Association of Obstetricians and Gynecologists.

Dr. Kennedy and her associates assessed the rates of painful bladder syndrome (interstitial cystitis) and irritable bowel syndrome in 324 women who were being treated at a vulvar disease clinic, and compared them with the rates among 321 control subjects attending a general gynecology clinic.

Of the women with vulvar disease, 12% reported bladder pain, compared with only 6% of control subjects. Similarly, 23% of those with vulvar disease were found to have bowel pain, compared with only 11% of control subjects.

Looked at another way, the data showed that women who reported bladder pain were 2.18 times more likely than were those who did not report bladder pain to have been treated for vulvar disease. Women with vulvar disease had a mean score of 20.3 on the Urinary Distress Inventory's pain subscale, compared with a mean score of 5.3 for women without vulvar disease.

Likewise, women with functional bowel disorders were 2.13 times more likely than were those who did not have bowel disorders to have been treated for vulvar disease.

The higher prevalence of painful bladder and painful bowel syndromes in women with vulvar disease may reflect a common etiology for all these disorders. The design of this study, however, didn't allow the researchers to tease out whether there is a common etiology "or whether treatments for one disorder may exacerbate or cause the other disorders.

"From a clinical point of view, it is clear that women with vulvar disease should be queried about bladder and bowel pain, and treated accordingly," Dr. Kennedy said.

She added that the study also showed that women with vulvar disease had nearly a fourfold higher risk of undergoing hysterectomy than did the general gynecology patients. "To our knowledge, ours is the first large clinic comparison to report this association," she said.


Contributing Writer

COPYRIGHT 2005 International Medical News Group
COPYRIGHT 2005 Gale Group

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