Huntington Disease Repeat Expansion Analysis

Casandra

Casandra Test Code BA15627Version 1 (DRAFT)

Performing Lab

Lab Baylor GeneticsLab Test ID 6034CPT Code 81271

Huntington Disease Repeat Expansion Analysis

Clinical Use

Use

The Huntington Disease Repeat Expansion Analysis is crucial in identifying the number of CAG repeats within the HTT gene, which is directly linked to Huntington disease (HD). This hereditary neurological disorder leads to a range of symptoms including chorea, cognitive impairments, and psychiatric issues, generally manifesting in mid-adulthood. Patients often experience personality changes, depression, and motor difficulties that escalate over time. There is significant variability in disease onset, influenced by the number of CAG repeats. Individuals with over 60 repeats may face early-onset HD, highlighting the importance of genetic counseling and informed reproductive choices.

Special Instructions

Testing is restricted to individuals aged 18 or older who are part of a facility with a documented procedure for predictive testing. It is imperative that the HD Indication and Informed Consent Form is included with both the specimen and requisition form to ensure proper processing and consent mechanisms are in place.

Limitations

While the analysis effectively quantifies CAG repeats, the interpretative scope may be influenced by the repeat number's variability and instability, particularly in the premutation range of 27-35 repeats. Results may not consistently predict onset age or disease severity. Furthermore, testing is not appropriate for individuals under the age of 18 or those without a relevant family history. Laboratory performance characteristics may vary and false negatives are possible, particularly with allele drop-out issues in some samples.

Test Details

New York Approved