PHOX2B Repeat Expansion Testing

Description

Pathogenic GCN repeat expansions within exon 3 of the PHOX2B gene have been associated with autosomal dominant congenital central hypoventilation syndrome (CCHS). Both neonatal and later onset (>1 month-adulthood) forms of the disorder have been reported.

Pathogenicity is dependent upon GCN repeat length according to the following ranges 1-3:

Normal Alleles

Mutable Normal Alleles

Intermediate/Uncertain Alleles

Reduced Penetrance Alleles

Full Penetrance Alleles

21 or fewer

-

22-23

-

24 or more*

*Longer repeats typically lead to more severe disease with neonatal onset 1,3,4.

Tests That Analyze PHOX2B Repeats