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Phenylketonuria Phenylketonuria
Phenylketonuria, more commonly referred to as PKU , is an inherited metabolic disorder. In the US at least 1 out of every 25,000newborns... Phenylketonuria

by Kimberly Allen R.N.

Phenylketonuria, more commonly referred to as PKU , is an inherited metabolic disorder.  In the US at least 1 out of every 25,000newborns are born with PKU.  This condition occurs in all ethnic groups, however it is more prevelant in people of Northern European and Native American descent.  Turkey has the highest incidence with 1 in every 2,600 births, other countries with a high incidence of PKU are Italy, China and Yemen.
In order to inherit PKU you have to inherit 2 abnormal genes, 1 from each parent.  If you inherit only 1 abnormal gene you will become a “carrier”.  Carriers have 1 normal gene and 1 abnormal gene therefor their health is not affected because the normal gene is able to cover for the mutated one.  If both parents are carriers there’s a 25% chance of recieving the abnormal genes from both parents resulting in PKU.   There is also a 50% chance of recieving 1 normal and 1 abnormal genes making you a carrier also and there’s a 25% chance of receiving the normal gene from both parents then you would be neither a carrier or have PKU.
PKU occurs when the gene resposible for the liver enzyme known as PAH is either absent or not working.  PAH is resposible for converting the amino acid phenylalanine into toe amino acid tyrosine.  When PAH is either not working at all or not working well the phenylalanine builds up and is then converted to pheylketone and is then detected in the urine.
The signs and symptoms of PKU can vary from mild to severe depending on the ability to tolerate phenylalanine.  Classic PKU is the most severe form of PKU.  IN infants that have not been tested and diagnosed with PKU there are usually no symptoms until they are a few months old.  At that you will start to notice they’re not accomplishing the developmental milestones when they should, they usually will have seizures and behavior problems.  Also, children that have classic PKU usually have lighter hair and skin thenother members of the family that don’t have PKU.
Left untreated PKU can lead to brain damage, including severe mental retardation, seizures as well as numerous other potentially serious conditions.  Fortunately in the US and many other countries all newborns are screened for PKU before they leave the hospital.  There are some that recommend that testing be repeated in 2-7 days if the baby wass tested in the first 24 hours after birth.
There is no cure for PKU, however when diagnosed early it can be managed with dietary modifications and oif needed a combination of medications and diet.  Infants can still be breast fed, but the quantity must be limited and monitored as well as supplements provided in order to provide the necrssary nutrients.  There are special supplementary formulas for infants to provide the nutrients that are missing in a low phenylalanine diet.  As your child grows and begins eating, as opposed to formula or breast feeding, the diet must be strictly monitored and involves severly restricting or avoiding foods like meat, chicken, fish, eggs, nuts, cheese, legumes, milk, and other dairy products that are high in phenylalanine.  Also, foods high in
starch like potatoes, pasta, bread, and corn need to be closely monitored.  There are also medications that can decrease the levels of phenylalanine levels in the blood. When diagnosed and monitored closely people born with PKU that strictly adhere to their can lead normal active lives.

Kimberly Allen is a registered nurse with an AND in nursing. She has worked in ACF, LCF and psychiatric facilities, although she spent most of her career as a home health expert. She is now a regular contributor to, dispensing advice and knowledge about medical issues and questions. You can reach her with any comments or questions at