Kennedy disease pathophysiology
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Overview
Pathophysiology
Genetics
The gene for the androgen receptor is located on the X chromosome (Xq11-q12), making it a sex-linked disease, thus KD generally affects males. Females are rarely affected; female carriers tend to have a relatively mild expression of the disease if they show symptoms at all.
- Homozygous females
Homozygous females, both of whose X chromosomes have a mutation leading to CAG expansion of the AR gene, have been reported to show only mild symptoms of muscle cramps and twitching. No endocrinopathy has been described.
Pathology
Kennedy disease, reported in 1991, involves multiplied CAG repeats in the first exon (trinucleotide repeats). Inheritance is X-linked recessive with anticipation. 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 mutaion 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. There is currently no treatment or cure for Kennedy's Disease.