Definition

Biallelic pathogenic variants in the PAH gene reduce the activity of phenylalanine hydroxylase, preventing the conversion of phenylalanine to tyrosine; phenylalanine then accumulates to toxic levels in the blood. Untreated classic PKU follows a course of progressive intellectual disability, seizures, and characteristically fair skin/hair color; early diagnosis through newborn screening and dietary treatment prevent these outcomes.

Gene/region examined

PAH - Exon 1, PAH - Exon 2, PAH - Exon 3, PAH - Exon 4, PAH - Exon 5, PAH - Exon 6, PAH - Exon 7, PAH - Exon 8, PAH - Exon 9, PAH - Exon 10, PAH - Exon 11, PAH - Exon 12, PAH - Exon 13

Method

Sequence 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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