Phenylketonuria (PKU)

     PKU is a very rare disorder, it only happens to 1 in 10,000 caucasians.  The percentage is a lot less with other races.  Most children are screened for PKU at birth.  If they aren't tested and they have the disorder the child will have a small head, epilepsy and mental retardation.  To screen the babies they test for high levels of phenylalanine in their blood.  If it is they have to make sure its not from another protein defect by BH4.  PKU occurs when a genetic mutation disrupts the function of a crucial metabolic enzyme PAH.  This makes high phenylalanine levels in the brain.  This poisons the neurons and causes mental retardations.  If a person has this disorder they should stay to a low protein diet until at least 12 years old and to be safe most people stay on it their whole lives.  It is a very rare disorder but if you have it, its not fun.