Definition

In approximately 96 percent of cases, a biallelic GAA trinucleotide repeat expansion is found in intron 1 of the FXN gene, which reduces production of the frataxin protein. Frataxin deficiency impairs iron-sulfur cluster biosynthesis and causes cell loss in the dorsal root ganglia and the cerebellar dentate nucleus, leading to progressive ataxia, dysarthria, cardiomyopathy, and skeletal deformities.

Gene/region examined

FXN - GAA repeat

Method

Fragment analysis

Accepted sample types

EDTA blood, AF, CVS

Inheritance

Hereditary, autosomal recessive.

Related Tests

Inheritance Patterns

Describes how a genetic condition is passed on within a family. There are five main patterns

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Carrier (Heterozygous / Homozygous)

Why it matters: In autosomal recessive inheritance, when each parent is a carrier (while both appear healthy), the chance of their child being born with the disease is 25% in each

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VUS (Variant of Uncertain Significance)

This is the situation where the test has detected a change in the DNA, but the role of this change in the development of disease is unconfirmed.

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How to Read a Genetic Test Result (Positive / Negative / VUS)

A genetic test result falls into three main categories

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Types of Genetic Tests

A genetic test is a type of medical test that detects changes in genes, chromosomes or proteins. Today there are more than 77,000 genetic tests available.

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