Medical Health Encyclopedia

Phenylketonuria

Injury Disease Nutrition Poison Symptoms Surgery Test Special Topic

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Phenylketonuria test Phenylketonuria test

Overview Symptoms Treatment Prevention

Phenylketonuria

Definition:

Phenylketonuria (PKU) is a rare hereditary condition in which the amino acid phenylalanine is not properly metabolized. PKU can cause severe mental retardation if not treated.

Alternative Names:
PKU

Text Continues Below

---

Causes, incidence, and risk factors:

Phenylketonuria (PKU) is inherited as an autosomal recessive trait (both parents must pass on the defective gene for the child to be affected). The genetically-determined abnormality in phenylketonuria is a missing enzyme called phenylalanine hydroxylase.

Phenylalanine is 1 of the 8 essential amino acids found in protein-containing foods. In PKU, phenylalanine cannot be used in a normal fashion because of the missing enzyme. Subsequently, high levels of phenylalanine, and 2 closely-related phenylalanine derivatives, build up in the body. These compounds are toxic to the central nervous system and cause brain damage.

Damage to the brain causes marked mental retardation by the end of the first year of life if the offending proteins are not scrupulously avoided. Older children may develop movement disorders (athetosis), rocking, and hyperactivity.

PKU is a treatable disease that can be easily detected by a simple blood test. Most states require a screening test for all newborns, generally done with a heelstick shortly after birth.

Because phenylalanine is involved indirectly in the production of melanin, the pigment responsible for skin and hair color, children with phenylketonuria often have lighter complexions than their unaffected siblings. There is a characteristic "mousy" odor that results from the accumulation of phenylacetic acid. This odor may be detected on the breath, skin, and urine if the condition has not been treated immediately from birth or if foods containing phenylalanine are consumed.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2004 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.