More About PKU

By- Erica Martin, Contributing Writer

There are many conditions that can affect babies from birth. One of the more rare conditions is phenylketonuria, or PKU.  This article will discuss what PKU is, the symptoms, diagnosis, treatment, prognosis and prevention, and how you can help raise money for PKU research.


What is PKU?

Phenylketonuria, or PKU, is a rare genetic condition in which a baby is born without an enzyme called phenylalanine hydroxylase. This enzyme is needed to break down phenylalanine, an essential amino acid found in protein.  Without this enzyme, phenylalanine levels, as well as levels of other closely related substances, build up in the body. High levels of these substances harm the central nervous system and cause brain damage.

In order for a baby to have PKU, both parents must pass on the defective gene.  If one parent has the gene and the other doesn’t, the baby will not be born with it.


What are the symptoms of PKU?

Infants with PKU have lighter skin, hair and eyes than their brothers and sisters that don’t have the condition – this is because phenylalanine plays a part in the production of melanin, the pigment responsible for skin and hair color.

Other symptoms include:

  • Delayed mental and social skills
  • Significantly smaller head size
  • Arms and legs make jerking movements.
  • Intellectual disabilities
  • Seizures
  • Skin rashes
  • Tremors
  • Unusual positioning of the hands.


In addition, if it isn’t treated or a child with PKU eats foods with phenylalanine, phenylalanine will build up in their body, causing a musty or mousy odor in their breath, on their skin and in their urine.


How is it detected?

Every US state requires infants to be tested for PKU.  This is done with a simple blood test. If this test comes back positive, more blood and urine tests are done to confirm the PKU diagnosis.


How is it treated?

PKU is treated with a diet that’s very low in phenylalanine, especially when the child is growing. A doctor or registered dietitian will prescribe and supervise this diet, and it must be strictly followed.  Those who continue to follow the diet when they become adults have better mental and physical health.  Foods containing significant amounts of phenylalanine include milk, eggs, and the artificial sweetener aspartame, among other things. A special formula called Lofenalac is made for infants who have PKU – it can be used throughout life as a protein source that is very low in phenylalanine, and balanced for the other essential amino acids, so people with PKU can still get all the nutrition they need. In addition, taking supplements such as fish oil to replace the long-chain fatty acids that are missing from a phenylalanine-free diet can help improve neurological development, including fine motor coordination. In addition, people with PKU may need other supplements, such as iron or carnitine.


What is the outlook for someone with PKU?

If the phenylalanine-free diet is started shortly after birth and followed throughout life, the outlook for a person with PKU is very good. If treatment is delayed or PKU goes untreated, an infant with PKU can develop intellectual disability by the end of their first year of life. Children with PKU that is left untreated can develop ADHD, as well as other intellectual problems.


How can I prevent my unborn child from developing PKU?

If you think you might carry the PKU gene, you can get an enzyme assay done to find out for sure. In addition, chorionic villus sampling can be done when a woman is pregnant to determine if the unborn baby has PKU.  It’s important that a pregnant woman who has PKU follows a strict diet low in phenylalanine both before and during pregnancy, because the build-up of phenylalanine will damage the developing baby even if they haven’t inherited the defective gene.


What can I do to help with PKU research?

If you’re interested in helping fund PKU research, click here and read about how one child raised money to help advance PKU research. If you think this is a cause you would be interested in donating to, click the “donate” button on that page.


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