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Phenylketonuria

An evidence-led atlas of PAH deficiency, phenylalanine accumulation, newborn confirmation, lifelong diet and medication, and preconception control.

phenylketonuria · PKU · phenylalanine hydroxylase deficiency

MONDO:0009861Public QA completeSource-bound · 4

Disease at a glance

Start with the essentials, then explore the patient and research views.

Public revision · 48a05f9e0ea1

Disease class
PKU is an inherited metabolic disorder in which impaired phenylalanine metabolism raises blood concentrations.
Core mechanism
It is caused by biallelic pathogenic PAH variants and is inherited in an autosomal-recessive manner.
Genes or cause
Untreated high phenylalanine can cause irreversible developmental, cognitive, behavioral, and neurologic injury.
Typical features
Most cases are detected by newborn screening before symptoms appear.
Variability
Even treated individuals may have residual risks involving executive function, attention, fine motor skills, and mental health.
Diagnosis
An out-of-range screen requires prompt plasma amino-acid testing and etiologic evaluation for biochemical confirmation.
Management
PAH genetic testing is recommended to confirm diagnosis, help anticipate treatment response, and support genetic counseling.
Treatment and research
Other causes of hyperphenylalaninemia must be assessed rather than assuming PAH deficiency from phenylalanine alone.
Reading evidence
Treatment centers on a phenylalanine-restricted medical diet and specialized protein substitute maintained lifelong.
Key caution
Sapropterin, pegvaliase, or other therapies are selected according to indication, response, and risk.

For patients and families

A structured guide for understanding the disease and preparing for clinical conversations.

At a glance

PKU is an inherited metabolic disorder in which impaired phenylalanine metabolism raises blood concentrations.

Most cases are detected by newborn screening before symptoms appear.

How the disease works

It is caused by biallelic pathogenic PAH variants and is inherited in an autosomal-recessive manner.

Untreated high phenylalanine can cause irreversible developmental, cognitive, behavioral, and neurologic injury.

Why experiences vary

Even treated individuals may have residual risks involving executive function, attention, fine motor skills, and mental health.

Diagnosis and management

An out-of-range screen requires prompt plasma amino-acid testing and etiologic evaluation for biochemical confirmation.

Treatment status

PAH genetic testing is recommended to confirm diagnosis, help anticipate treatment response, and support genetic counseling.

Other causes of hyperphenylalaninemia must be assessed rather than assuming PAH deficiency from phenylalanine alone.

Reading clinical trials

People planning pregnancy should achieve and maintain target phenylalanine before conception and during pregnancy to reduce fetal risk.

Topics for a clinical visit

Clinical discussion should cover current phenylalanine and trend, diet and medicine adherence, nutrition, mental health, and pregnancy plans.

Medical notice

This material is for disease education and is not a personal diagnosis or treatment instruction.

Evidence and sources

A trial registry status does not establish efficacy or regulatory approval.