Huntington disease is caused by an abnormal expansion of a CAG repeat within the HTT/ITI5 on chromosome 4. Although the number of CAG repeats correlates with the age of onset, the correlation is not precise enough to use in determining disease prognosis for an individual patient.
Due to the complexities and ethical issues surrounding genetic testing for Huntington, a signed consent form for Huntington disease testing is mandatory. Please call our laboratory to review your patient's case in advance and obtain the necessary forms.
Click here for the GeneReviews summary on this condition.
This test is indicated for:
- Confirmation of a clinical diagnosis of Huntington disease
- Presymptomatic testing in adults with a family history of Huntington disease
Detection and Reference Range
Nearly 100% of CAG expansions in the HTT/ITI5 gene will be detected by this assay.
Normal individuals have 6-35 repeats while individuals with greater than 39 CAG repeats have a high probability of developing the disease. When the repeat number is between 36 and 39, Huntington disease cannot be reliably diagnosed due to incomplete penetrance.
Type: Whole Blood
Specimen Requirements:In EDTA (purple top) tube:
Infants (<2 years): 2-3 ml
Children (>2 years): 3-5 ml
Older Children & Adults: 5-10 ml
Specimen Collection and Shipping: Refrigerate until time of shipment. Ship sample within 5 days of collection at room temperature with overnight delivery.