HTT Repeat Expansion Testing

Description

Pathogenic CAG repeat expansions in the HTT gene have been associated with autosomal dominant Huntington disease (HD). The pathogenic repeat expansions are translated into polyglutamine tracts, causing toxic effects that dysregulate essential cellular processes, and lead to cell death.

Pathogenicity is dependent upon CAG repeat length according to the following ranges ^1-2:

*Mutable normal alleles may expand or contract in subsequent generations.

**Juvenile onset Huntington disease is associated with 61 CAG repeats or more.