Phenylketonuria (PKU) is a genetic disorder (a disease a person is born with) where a person's body cannot break down an amino acid called phenylalanine. Amino acids are necessary to make proteins, an important part of the human body. Phenylalanine only comes from the food we eat; our bodies do not make any by themselves.

How it works 

Average people produce an enzyme called phenylalanine hydroxylase in their bodies. When they ingest phenylalanine, the body cannot use it, so this enzyme changes phenylalanine into tyrosine, which the body can use. In people with PKU, very little or no enzyme is made. Since the phenylalanine they eat is not being changed into tyrosine, it builds up in their bodies. This can cause problems with the way their bodies work.

Symptoms  
Symptoms vary from person to person. Because of the rarity of PKU, many symptoms go undiagnosed or unrecognized. In addition, there are variations in the categories of PKU individuals. There are untreated, early treated, late treated, those returning to diet, Hyperphe, Classical PKU, uncontrolled, and highly controlled. For your average infant a doctor will diagnose PKU with a quick blood test. Their symptom will be high PHE levels. If that infant goes undiagnosed for weeks or months, he/she may start to exhibit some or all of the following symptoms for uncontrolled PKU. The symptoms include:

 focus/concentration problems 
 seizures
 lowered intelligence
 tremors
 problems with memory 
 gait (walking) problems
 anxiety
 skin problems
 depression 
 mousy odor
 aggression
 irritability
 phobias 
 mental fog
 slower thinking and response 
 hyperactivity
 lethargy
 social anxiety
 decreased motor function and hand/eye coordination
 fatigue
 psychotic symptoms
 mild paralysis
 autistic behaviors
 social withdrawals 
 lack of autonomy
 social maturity deficits 
 decreased positive emotions
 low self-esteem

Treatment 

Today, scientists know what foods have phenylalanine in them, and they have created a special diet for people with PKU. Since they cannot use it, people with PKU cannot eat foods that have a lot of phenylalanine, like eggs, meat and milk. An artificial sweetener called aspartame is also a source of phenylalanine. People with PKU take a lot of vitamins to make up for the foods they cannot eat, especially vitamins B6 and B12.

Babies with PKU are fed a special formula.  It has everything babies need to stay healthy, but with very little phenylalanine. There are also low protein foods like breads and flour (Made from corn and starch instead of regular wheat).

Women with PKU who are pregnant or trying to get pregnant have to be especially careful to follow this diet. If they do not follow the diet, their babies could be born with severe birth defects and mental retardation. Babies born to women with PKU who have followed the PKU diet throughout their pregnancy are usually healthy and do not necessarily but may develop PKU. Whether or not they have PKU themselves depends on the mother and father's genes. In fact there are people who are Carriers  (Dormant Genes) that can be passed on until they resurface in the future generations. These are so far undetectable, However, since PKU is genetically recessive it takes PKU genes from both parents to cause PKU.

PKU kids usually have light hair and eyes due to the effect of phenylalanine in the production of melanin.  They also tend to have very fair skin which can cause them to burn easily. Solar protection is a must for those who wish to work, play, or engage in activities outdoors.

Future 

Most people with PKU can live as long and healthy as anyone else if the low-phenylalanine diet is started when they are babies and continued for the rest of their lives. The symptoms will usually disappear after the diet is started.

Other websites 
 
Genetic disorders