Friedreich Ataxia, Repeat Expansion Analysis, Varies

Casandra

Casandra Test Code MC24516Version 1 (DRAFT)

Performing Lab

Lab Mayo Clinic LabLab Test ID AFXNCPT Codes 81265, 81284, 88233, 88235, 88240

Friedreich Ataxia, Repeat Expansion Analysis, Varies

Clinical Use

Use

This test is useful for the molecular confirmation of clinically suspected Friedreich ataxia. It assesses for GAA trinucleotide repeat expansions within the FXN gene to confirm a molecular diagnosis. Friedreich ataxia is a progressive hereditary ataxia characterized by gait and limb ataxia, dysarthria, and sensory loss, often accompanied by cardiomyopathy and diabetes mellitus. The majority of individuals affected by Friedreich ataxia exhibit homozygous GAA trinucleotide repeat expansions in intron 1 of the FXN gene. This analysis is significant for categorizing the size of the repeat expansions, which correlates with the onset and severity of the disease.

Special Instructions

Not provided.

Limitations

The assay will not detect nonrepeat expansion variants such as sequence variants, deletions, and duplications. Errors in test interpretation may occur if the provided information is inaccurate or incomplete. Bone marrow transplants from allogenic donors will interfere with testing, as results may not reflect true GAA repeat sizes in other tissues. Some prenatal specimen tests will add additional charges for culture, as well as maternal cell contamination studies. The GAA-repeats size in peripheral blood specimens may not fully represent the size in other tissues due to somatic mosaicism.

Test Details

New York Approved