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HUNTINGTON DISEASE

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Huntington Disease (HD) is a progressive disorder of motor, cognitive, and psychiatric disturbances. The mean age of onset is 35 to 44 years; this is modified by the repeat length, epigenetic influences, and possibly environmental influences. The median survival time is 15 to 18 years after onset. Chorea, an involuntary movement disorder consisting of non-repetitive, non-periodic jerking of limb, face, or trunk, is the major sign of the disease. This disease occurs in 3-7 people per 100,000, in populations of western European descent. The disease is inherited in an autosomal dominant fashion, and is caused by the expansion of CAG trinucleotide repeats in exon 1 of a gene termed Huntingtin (HTT, originally known as IT-15) on chromosome 4p16.3. This trinucleotide codes for the amino acid glutamine.

A normal allele for gene IT15 contains 10-26 CAG repeats. Individuals with 27-35 repeats fall into the intermediate range, and their children are at risk of HD. The abnormal range varies between 36-121 alleles; individuals at the bottom of this range may or may not develop symptoms of HD. Expansions greater than 60 repeats result in juvenile onset, while expansions between 40 and 55 repeats induce adult onset. Repeats between 27 and 35 can be meiotically unstable in paternal transmission. Descendants of men with repeats in this range have been known to inherit repeats of 40 or more, which are associated with the disease.

Adellgene Huntington Disease (HD) is an in vitro diagnostic kit which detects the number of repetitions of the CAG triplet, located on exon 1 of the IT15 gene (HTT), which can result in the formation of Huntington’s disease. The technology is based on the polymerase chain reaction (PCR) of genomic DNA, extracted and purified from peripheral blood, followed by fluorescence analysis of the size of the PCR fragments obtained by the genetic analyzer and conversion of that size into the respective number of CAG repeats.