What is it?

Phenylketonuria, also called PKU, is a rare inherited disorder that causes an amino acid called phenylalanine to build up in the body. PKU is caused by a defect in the gene that helps create the enzyme needed to break down phenylalanine. Without the enzyme necessary to process phenylalanine, a dangerous buildup can develop when a person with PKU eats foods that contain protein or eats aspartame, an artificial sweetener. This can eventually lead to serious health problems. For the rest of their lives, people with PKU - babies, children, and adults - need to follow a diet that limits phenylalanine, which is found mostly in foods that contain protein.

18 Alikes with Phenylketonuria (PKU)

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Phenylketonuria (PKU).

Additional names

This group contains additional names:
- Dihydropteridine reductase deficiency
- Guanosine triphosphate cyclohydrolase I deficiency
- Hyperphenylalaninemia
- Pterin-4-carbinolamine dehydratase deficiency
- Transient hyperphenylalaninemia

Signs & symptoms

PKU signs and symptoms can be mild or severe and may include:
- A musty odor in the breath, skin or urine, caused by too much phenylalanine in the body
- Neurological problems that may include seizures
- Skin rashes (eczema)
- Fair skin and blue eyes, because phenylalanine can't transform into melanin - the pigment responsible for hair and skin tone
- Abnormally small head (microcephaly)
- Hyperactivity
- Intellectual disability
- Delayed development
- Behavioral, emotional, and social problems
- Psychiatric disorders


Newborn blood testing identifies almost all cases of phenylketonuria. A PKU test is done a day or two after the baby's birth. The test is done after the baby is 24 hours old and after the baby has ingested some protein in the diet to ensure accurate results.
- A nurse or lab technician collects a few drops of blood from the baby's heel or the bend in the baby's arm.
- A laboratory tests the blood sample for certain metabolic disorders, including PKU.


The main treatment for PKU includes:
- A lifetime diet with a very limited intake of protein, because foods with protein contain phenylalanine
- Taking a PKU formula- a special nutritional supplement - for life to make sure getting enough essential protein (without phenylalanine) and nutrients that are crucial for growth and general health

☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.

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