A genetic metabolic disturbance characterized by an inability to convert phenylalanine to tyrosine. It is treatable by diet when detected in early infancy; if untreated, intellectual disability results. Also known as phenylpyruvic oligophrenia.
A genetic disease caused by a recessive gene that results in an infant being unable to metabolize phenylalanine, an essential amino acid that is present in milk. It is characterized by the absence of the enzyme phenylalanine hydroxylase that is normally present in the liver. As a result, phenylketone bodies are formed that damage brain cells resulting in mental retardation can be detected by the Guthrie blood test shortly after birth and, when positive, measures can be taken to prevent the onset.
A hereditary condition which affects the way in which the body breaks down phenylalanine, which in turn concentrates toxic metabolites in the nervous system causing brain damage.
A genetic disease due to a mutation in the gene for the enzyme phenylalanine hydroxylase. Several variants have been described. The phenotypic expression of the genotype includes mental retardation. Expression can be prevented by early diagnosis and use of a low phenylalanine diet.
Phenylketonuria (PKU) is the most common of all aminoacidopathies and is caused by autosomal recessive deficiency of the hepatic phenylalanine hydroxylase system. This metabolic abnormality results from a markedly reduced activity (< 2% of normal) of phenylalanine hydroxylase, the hepatic enzyme that converts phenylalanine to tyrosine. The deficiency of this enzyme results in toxic levels of phenylalanine in the blood and a-potential deficiency of the amino acid tyrosine. If treatment is not begun in the early days following birth, mental retardation, microcephaly, epilepsy, tremors, hypopigmentation of skin, and hyperactivity can occur.
A genetic disorder in which children have a defect in the liver enzyme that normally converts the protein phenylalanine into a useful form. In children with PKU, the phenylalanine (sometimes abbreviated as “phe”) builds up in the bloodstream, blocking normal development of the brain. The defect affects at least one baby in every 16,000, most commonly those of northern European background, less often those of Jewish, Asian, or African descent. Undetected, PKU can cause mental retardation by the time a child is one year old; if detected but not properly treated or responsive to treatment, it can lead to behavioral disturbances and learning disabilities. To prevent this, the Guthrie (PKU) test is routinely given (often by law) to newborns; a few drops of blood taken from the baby’s heel will show if there is excess phenylalanine in the blood. Treatment involves a diet low on foods with phenylalanine, such as cow’s milk, meat, regular formula, and other protein-rich foods, with regular monitoring of the blood’s phenylalanine level. Infants may be given a special formula containing no phenylalanine; later the child is well-advised to follow a low-protein, largely vegetarian diet. Most cases of PKU respond to such a diet, but how long the diet should be maintained is controversial. In practice, many children go off the special diet on reaching their teens. Women who have PKU must be extremely careful to maintain a low-protein diet during pregnancy—or when there is a possibility that they may become pregnant—because the buildup of phenylalanine can cause irreparable brain damage to the fetus in the uterus. This is a special problem because some women were never told that they had PKU and may not remember being on a special diet when young.
Genetic disorder in which the absence of, or a deficiency in, the enzyme necessary for conversion of the amino acid phenylalanine into tyrosine causes the accumulation of phenylalanine and its metabolites in the body and the urine. Symptoms include eczema, an unusual odor to the urine, and progressive mental retardation. Treatment includes a diet low in, or free of, phenylalanine. Most states routinely test newborns for the defect; the test is referred to as the PKU test.
A congenital disorder resulting in the inability to metabolize the amino acid phenylalanine due to the deficiency of the enzyme phenylalanine hydroxylase, causing severe neurological, skin, and psychiatric disorders; treatment consists of dietary restriction of phenylalanine.
An inborn defect of protein metabolism causing an excess of the amino acid phenylalanine in the blood, which damages the nervous system and leads to severe mental retardation. Screening of newborn infants by testing a blood sample for phenylalanine (the Guthrie test) enables the condition to be detected soon enough for dietary treatment to prevent any brain damage: the baby’s diet contains proteins from which phenylalanine has been removed. The gene responsible for phenylketonuria is recessive, so that a child is affected only if both parents are carriers of the defective gene.
Commonly referred to as PKU, this is a metabolic cause of learning disability. The incidence in Europeans is around 1 in 15,000 births. It is due to the inability of the baby to metabolize the amino acid, phenylalanine. In many countries, every newborn baby is screened for PKU by testing a spot of their blood. A positive diagnosis leads to lifelong treatment with a diet low in phenylalanine, with a good chance that the infant will grow up mentally normal. Parents of children with phenylketonuria can obtain help and information from the National Society for Phenylketonuria.
A congenital autosomal recessive disease marked by failure to metabolize phenylalanine to tyrosine. It results in severe neurological deficits in infancy if it is unrecognized or left untreated. PKU is present in about 3.5 in 10,000 newborns in the U.S. In this disease, phenylalanine and its by-products accumulate in the body, especially in the nervous system, where they cause severe mental retardation (IQ test results often below 40), seizure disorders, tremors, gait disturbances, coordination deficits, and psychotic or autistic behavior. Eczema and an abnormal skin odor also are characteristic. The consequences of PKU can be prevented if it is recognized in the first weeks of life and a phenylalanine restricted (very low protein) diet is maintained throughout infancy, childhood, and young adulthood.
A recessive genetic disorder in which the body cannot break down phenylalanine; it can cause mental retardation.
A genetic disorder in which the body lacks an important enzyme. If untreated, the disorder can lead to brain damage and intellectual disabilities (ID).
A hereditary condition characterized by a malfunctioning enzyme responsible for transforming the amino acid phenylalanine into another amino acid called tyrosine. If phenylalanine isn’t restricted from the diet, it accumulates in the body and leads to profound learning challenges. As a standard procedure, all newborn infants undergo the Guthrie test, involving a blood sample, to screen for phenylketonuria.
Infants who are impacted by this condition initially exhibit minimal indications of abnormality. However, without the exclusion of phenylalanine from their diet, they experience neurological disruptions, often leading to epilepsy. These babies commonly possess blonde hair and blue eyes, with their urine emitting a distinct musty scent. Additionally, many of them present the skin condition eczema.
Phenylalanine is present in numerous protein-containing foods, as well as in artificial sweeteners. Typically, a customized diet is advised for an individual’s entire life, with particular emphasis on adhering to this diet during pregnancy. This is crucial since elevated phenylalanine levels in the mother could harm the developing fetus.