Disease Overview:

Hyperphenylalaninaemia (HPA) is an umbrella term referring to medical conditions that lead to abnormally high levels of phenylalanine (Phe).The most common cause of HPA is phenylalanine hydroxylase (PAH) deficiency, which is caused by a mutation in the PAH gene resulting in loss of function of PAH. Which is the metabolism of Phe to tyrosine (Tyr).The terms ‘PAH deficiency’ and ‘PKU’ are sometimes used interchangeably.

HPA can also be the result of tetrahydrobiopterin (BH4) deficiency, caused by dysfunction of genes involved in BH4 synthesis or regeneration which is a cofactor required by PAH for the metabolism of Phe to Tyr.

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