Best practice guide for adults
The heredity of PKU: the risk of passing it on
For a child to be born with the disorder, both parents must be a carrier of the gene.
Phenylketonuria (PKU) develops when the gene that provides the blueprint for production of an enzyme called Phenylalanine Hydroxylase (PAH) is defective. Everyone has two genes for PAH. In order for PKU to develop, both of these genes must be defective.
A person with one defective gene is a PKU carrier and does not have PKU, but may pass the defective gene on to his/her children. This means that if both parents are carriers and the child inherits both defective genes, he or she will have the disorder.
The following diagrams illustrate the possible genetic outcomes.
Ethnicity as a factor: the incidence of PKU in Europe
The incidence of Phenylketonuria (PKU) varies considerably between ethnic groups.
A diagnosis of the disorder occurs in about 1 in 10,000 Caucasian or East Asian births. Some ethnic groups have lower rates, like the Japanese (1 in 143,000) and some higher, such as the Irish (1 in 4,500) and Turkish (1 in 2500), PKU is rare among Africans.
| Country | Prevalence (screened/
diagnosed) |
|---|---|
| England | 1:10000 |
| Northern | 1:4500 |
| France | 1:17769 |
| Italy | 1:3654 |
| Spain | 1:6532 |
| Germany | 1:8553 |
