Phenylalanine hydroxylase deficiency is an inherited disorder caused by the buildup of phenylalanine (an amino acid) in the blood. Affected people carry genetic variants of the PAH gene, which reduce the activity of the phenylalanine hydroxylase enzyme, leading to a buildup of phenylalanine and the characteristic symptoms of intellectual disability and other health problems. This condition is also known as phenylketonuria or PKU.
Take this test to find out if you are a genetic carrier of a PAH variant and are at risk of passing it to your children.
Phenylalanine hydroxylase deficiency is caused by genetic variation in the PAH gene. This gene gives instructions to make the phenylalanine hydroxylase enzyme involved in the breakdown of phenylalanine.
Affected people produce a phenylalanine hydroxylase enzyme with reduced activity, leading to a buildup of phenylalanine. The cells in the brain are the most affected as phenylalanine accumulation leads to the destruction of the fatty covering (myelin) of nerve cells. More than 900 PAH variants have been identified, affecting enzyme activity to different degrees, accounting for the variable severity of this disorder.
Phenylalanine hydroxylase deficiency is inherited in an autosomal recessive pattern, which means two defective copies of the PAH gene must be inherited in order for symptoms to appear.
This test detects 23 genetic variants in the PAH gene that occur more commonly in people of Irish, Turkish, East Asian and European descent.
Understanding your carrier status for phenylalanine hydroxylase deficiency will help you understand the risk of passing a variant to your children.
Based on disease severity, phenylalanine hydroxylase deficiency can be distinguished into two types: classic PKU and variant PKU. Classic PKU is the most severe form and often presents with the following symptoms:
- Intellectual disability
- Behavioural problems
- Decreased hair and skin pigmentation
How It Works
Step 1: Sign up for a free DNA Access account.
Step 2: Upload your DNA markers to DNA Access.
Step 3: Log in to your account to access your results when they are ready.