Phenylketonuria PKU; Neonatal phenylketonuria
Last reviewed: June 17, 2011.
Phenylketonuria (PKU) is a rare condition in which a baby is born without the ability to properly break down an amino acid called phenylalanine.
Causes, incidence, and risk factorsPhenylketonuria (PKU) is inherited, which means it is passed down through families. Both parents must pass on the defective gene in order for a baby to have the condition. This is called an autosomal recessive trait.Babies with PKU are missing an enzyme called phenylalanine hydroxylase, which is needed to break down an essential amino acid called phenylalanine. The substance is found in foods that contain protein.
Without the enzyme, levels of phenylalanine and two closely-related substances build up in the body. These substances are harmful to the central nervous system and cause brain damage.
SymptomsPhenylalanine plays a role in the body's production of melanin, the pigment responsible for skin and hair color. Therefore, infants with the condition often have lighter skin, hair, and eyes than brothers or sisters without the disease.Other symptoms may include:
Delayed mental and social skills
Head size significantly below normal
Hyperactivity
Jerking movements of the arms or legs
Mental retardation
Seizures
Skin rashes
Tremors
Unusual positioning of hands
If the condition is untreated or foods containing phenylalanine are not avoided, a "mousy" or "musty" odor may be detected on the breath and skin and in urine. The unusual odor is due to a build up of phenylalanine substances in the body.
Signs and testsPKU can be easily detected with a simple blood test. All states in the US require a PKU screening test for all newborns as part of the newborn screening panel. The test is generally done by taking a few drops of blood from the baby before the baby leaves the hospital.If the initial screening test is positive, further blood and urine tests are required to confirm the diagnosis.
TreatmentPKU is a treatable disease. Treatment involves a diet that is extremely low in phenylalanine, particularly when the child is growing. The diet must be strictly followed. This requires close supervision by a registered dietitian or doctor, and cooperation of the parent and child. Those who continue the diet into adulthood have better physical and mental health. "Diet for life" has become the standard recommended by most experts. This is especially important before conception and throughout pregnancy.Phenylalanine occurs in significant amounts in milk, eggs, and other common foods. The artificial sweetener NutraSweet (Aspartame) also contains phenylalanine. Any products containing aspartame should be avoided.
A special infant formula called Lofenalac is made for infants with PKU. It can be used throughout life as a protein source that is extremely low in phenylalanine and balanced for the remaining essential amino acids.
Taking supplements such as fish oil to replace the long chain fatty acids missing from a standard phenylalanine-free diet may help improve neurologic development, including fine motor coordination. Other specific supplements, such as iron or carnitine, may be needed.
Expectations (prognosis)The outcome is expected to be very good if the diet is closely followed, starting shortly after the child's birth. If treatment is delayed or the condition remains untreated, brain damage will occur. School functioning may be mildly impaired.If proteins containing phenylalanine are not avoided, PKU can lead to mental retardation by the end of the first year of life.
ComplicationsSevere mental retardation occurs if the disorder is untreated. ADHD (attention-deficit hyperactivity disorder) appears to be the most common problem seen in those who do not stick to a very low-phenylalanine diet. Calling your health care providerCall your health care provider if your infant has not been tested for PKU. This is particularly important if anyone in your family has the disorder. PreventionAn enzyme assay can determine if parents carry the gene for PKU. Chorionic villus sampling can be done during pregnancy to screen the unborn baby for PKU.It is very important that women with PKU closely follow a strict low-phenylalanine diet both before becoming pregnant and throughout the pregnancy, since build-up of this substance will damage the developing baby even if the child has not inherited the defective gene.
ReferencesReview Date: 6/17/2011.
Reviewed by: Kimberly G Lee, MD, MSc, IBCLC, Associate Professor of Pediatrics, Division of Neonatology, Medical University of South Carolina, Charleston, SC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
A genetic disorder in which the essential digestive enzyme phenylalanine hydroxylase is missing is known as Phenylketonuria (PKU). This leads to a buildup of phenylalanine in the body, which can be toxic to the brain if not managed properly through a restricted diet low in phenylalanine.
Enzyme replacement therapy is generally effective in treating enzyme deficiencies by providing the missing enzyme to the body. It can help improve symptoms and quality of life for patients with enzyme deficiencies.
If an enzyme is not present in the body, the specific biochemical reaction that the enzyme catalyzes will not occur efficiently or at all. This can lead to a buildup of substrates, causing metabolic imbalances and potential health issues. Enzyme deficiencies can result in conditions such as lactose intolerance or phenylketonuria.
If an enzyme in a sequence of enzyme-controlled reactions is missing or defective then the process will stop at that point. So respiration could proceed until it reached the reaction which needed the missing or defective enzyme at which point it would stop.
PKU or phenylketonuria is caused by mutations in the gene that helps make an enzyme called phenylalanine hydroxylase or PAH. This enzyme is needed to convert the amino acid phenylalanine into other forms that the body uses and needs. When this gene is mutated the body can't break down foods that are high in protein such as milk, cheese, nuts, or meat.
Phenylketonuria
A genetic disorder in which the essential digestive enzyme phenylalanine hydroxylase is missing is known as Phenylketonuria (PKU). This leads to a buildup of phenylalanine in the body, which can be toxic to the brain if not managed properly through a restricted diet low in phenylalanine.
Phenylketonuria (PKU) is caused by mutations in the PAH gene, which provides instructions for making an enzyme called phenylalanine hydroxylase. This enzyme is essential for the breakdown of the amino acid phenylalanine. Mutations in the PAH gene lead to a deficiency in this enzyme, resulting in a build-up of phenylalanine in the body.
yes, phenylketonuria progressively leads to mental retardation. In phenylketonuria, there is lack of enzyme phenylalanine oxidase which generally oxidises phenylalanine to tyrosine. Hence, accumulation of phenylalanine occurs. This leads to a mousy smell a well as mental retardation.
The best treatment of phenylketonuria is a diet that is extremely low in phenylalanine during childhood. A person can also take fish oil supplements and iron supplements to help treat some of the symptoms.
prior to birth, the mother's enzyme level prevents accumulation of the dangerous chemical.
phenylketonuria
phenylketonuria
The enzyme phenylalanine hydroxylase breaks down phenylalanine into tyrosine. This enzyme is essential for the conversion of phenylalanine to tyrosine in the body. Deficiency in this enzyme can lead to a build-up of phenylalanine, which can result in a condition called phenylketonuria (PKU).
If an enzyme in a sequence of enzyme-controlled reactions is missing or defective then the process will stop at that point. So respiration could proceed until it reached the reaction which needed the missing or defective enzyme at which point it would stop.
If an enzyme in a sequence of enzyme-controlled reactions is missing or defective then the process will stop at that point. So respiration could proceed until it reached the reaction which needed the missing or defective enzyme at which point it would stop.
Phenylketonuria (PKU) is a recessive disorder caused by the absence of the enzyme phenylalanine hydroxylase, which converts phenylalanine to tyrosine. This leads to a buildup of phenylalanine in the body, causing intellectual disability and other complications if not managed through a restricted diet.