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HUNTINGTON'S DISEASE ANALYSIS BY PCR

Test Code: HUNT
Description: Huntington's Disease is an autosomal dominant neurodegenerative fatal disorder characterized by loss of striatal neurons. Symptoms of Huntington's Disease include chorea, psychiatric problems, ataxia, and cognitive disability. The disease is caused by an expanded, unstable trinucleotide repeat in the HTT gene on chromosome 4, which translates as an expanded polyglutamine repeat in the protein product (huntingtin). Individuals with repeat numbers of 40 or more will all eventually develop symptoms of Huntington's Disease. Individuals with repeat sizes between 27 and 35 will not develop Huntington"s Disease but their repeats may expand in future generations, particularly during male meiosis. Individuals with expansions between 36 and 39 may or may not develop Huntington's Disease symptoms and there is a risk for repeat expansion in future generations.

The Huntington's Disease test for expanded CAG repeats may be used for diagnosis of Huntington's Disease in individuals who have symptoms of the disease whether or not they have a family history of the disease. It may also be used to test asymptomatic individuals who have a family history of Huntington's Disease. These individuals must be over the age of 18 years and must provide informed consent for testing before the Huntington's Disease test is performed.

The expanded CAG allele associated with Huntington's Disease is detected by PCR amplification of the CAG repeat region and the number of CAG repeats usually can be accurately quantified using capillary electrophoresis. If clinical suspicion for Huntington's Disease is high and an expanded allele is not detected by any of the PCR reactions, a specimen may be sent out for Southern blot analysis.


 
 


 
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