ARX Repeat Expansion Testing

Description

Pathogenic GCN repeat expansions in the ARX gene have been associated with a spectrum of X-linked complex neurodevelopmental disorders including developmental and epileptic encephalopathy 1, X-linked intellectual developmental disorder 29, and Partington syndrome. The pathogenic repeat expansions lead to expanded polyalanine tracts that are thought to reduce the amount of functional ARX, which may impair neural migration during development.

Pathogenicity of GCN repeats in the first polyalanine tract is dependent upon length according to the following ranges ^1-3:

Pathogenicity of GCN repeats in the second polyalanine tract is dependent upon length according to the following ranges ^1-3:

Note: In targeted gene panels, ARX repeat expansions will be reported only in cases where the clinical symptoms of the patient include early-onset seizures.