Molecular Genetics Clinical Laboratory- Huntington Disease
INDICATIONS FOR TESTING:
Huntington disease (HD) is a slowly progressive disease involving emotional distress, involuntary movements and progressive mental and physical incapacitation affected 1/10,000 persons. HD is inherited in an autosomal dominant manner, with each child of an affected person having a 50 percent risk of inheriting HD. Both males and females are equally at risk. The average age of the onset of symptoms is 35 to 45 years and the average disease course is 15 to 20 years. Although a "typical" form of the disease is often described, there is considerable variation in severity between families. There is also variation in severity within families, especially if transmission is through affected males, occasionally resulting in juvenile-onset or childhood-onset HD.
Approximately 99% of affected individuals have an expansion of a trinucleotide CAG repeat pattern in the huntington gene localized to chromosome 4p1.6 that can be accurately measured. The repeat length is up to 25 in normal individuals, and from 39 to over 100 in affected persons. Individuals with repeats between 25 and 34 have not been found with symptoms of HD, although some variable symptoms have been reported for repeat lengths from 35 to 39. However, these intermediate repeat lengths from 25 to 39 have been shown to be unstable and their children are at increased risk for HD.
Most testing is completed within a time of 21 days following specimen receipt. Prenatal testing is usually completed within 7 days from specimen receipt.
Molecular testing for HD is based on the protocol established by the Huntington Disease Society of America.
Adult at 50% risk are tested in conjunction with personal genetic counselling, psychological screening and possibly neurological evaluation.
Specimens of 4 cc whole blood in EDTA tubes are accepted from symptomatic adults under the care of neurologists following counselling and informed consent.
Specimens from minors are not accepted in the absence of clinical symptoms.
The cost of testing is available upon request.
FOR MORE INFORMATION, PLEASE CONTACT:
Phone: (727) 767-8985 (Laboratory)
(727) 767-8611 (Director)
Fax: (727) 767-8367
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