What is it? What are the symptoms? What are the treatments?

What is phenylketonuria?

PKU is a rare inherited metabolic disorder which results when both parents are carriers of this affected gene. Affected people have a deficiency in the enzyme phenylalanine hydroxylase. This enzyme is needed to break down an essential amino acid called Phenylalanine into building blocks for several neurotransmitters in the brain.

A lack of phenylalanine hydroxylase means that, left uncontrolled, Phe builds up in the bloodstream, from where it can cause serious damage, especially to the brain. There's no cure for PKU, and it occurs in one about in 10,000 people, but there are management strategies to help prevent problems occuring.

Antenatal screening is available for PKU and all newborns are checked for the condition via the heel prick test (newborn blood spot test).

What are the symptoms of Phenylketonuria?

Developmental delay and reduced social skills, head size significant'y below normal, hyperactivity, seizures, skin rashes and tremors. Children with PKU often have lighter hair skin and eyes and if phenylalanine is not avoided in the diet, may develop musty-smelling breath, skin and urine.

What are the treatments and remedies of Phenylketonuria?

Treatment of PKU is extremely specialised and is a treatable disease. The main basis of treatment is a strictly controlled diet, which is low in protein and includes specially prescribed substitutes for this important nutrient. The artificial sweetner aspartame also contains phenylalanine and should be avoided. Deviation from the diet can lead to poor concentration, poor memory and a lack of organisational skills in affected children. Speech delay can also occur as well as emotional instability and general anxiety. However, adhering to the diet strictly means that affected children can develop normally.

This guide 

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Further help

For health advice and information 24 hours a day, 365 days a year, the NHS offers call and web services. You can also visit NHS websites for services, health information and health news at nhs.uk 

  • England – call 111 from any landline or mobile phone free of charge, or visit nhs.uk 
  • Scotland – call 111 from any landline or mobile phone free of charge, or visit nhs24.com 
  • Wales – call 0845 4647 , or visit nhsdirect.wales.nhs.uk 
  • Northern Ireland – visit hscni.net