Phenylketonuria will be fine when grown up, right?

Written by Zeng Hai Jiang
Pediatrics
Updated on May 04, 2025
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Phenylketonuria is an autosomal recessive genetic disorder, a congenital amino acid metabolism disorder caused by mutations in the phenylalanine hydroxylase gene. This mutation leads to decreased enzyme activity, causing phenylalanine and its metabolic products to accumulate in the body, thereby causing the disease. If diagnosed and treated early, a child's intelligence can remain normal, and abnormalities in the electroencephalogram can be restored. If uncontrolled, typical symptoms will appear as the child grows, including delayed growth and development, primarily manifested as delayed intellectual development, as well as seizures, light brown hair, and other symptoms.

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Written by Zeng Hai Jiang
Pediatrics
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What tests do parents with phenylketonuria undergo?

Parents with phenylketonuria can undergo chromosome testing. Phenylketonuria is a common amino acid metabolic disease and an autosomal recessive genetic disorder. Currently, it is mainly screened after the birth of the child by testing the blood for phenylketonuria. Phenylketonuria can also be screened prenatally before the birth of the newborn. Screening can be conducted by extracting amniotic fluid from the pregnant woman for genetic screening through amniocentesis between the 16th and 20th weeks of pregnancy. If chromosomal abnormalities are detected through amniocentesis, it indicates that the fetus carries the pathogenic gene, proving that the child will have phenylketonuria after birth. Couples carrying related genes also need to undergo prenatal screening.

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Written by Zeng Hai Jiang
Pediatrics
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What foods should children with phenylketonuria eat?

Phenylketonuria is a common amino acid metabolic disorder, an autosomal recessive genetic disease, and a type of hereditary metabolic disease that can be treated through dietary control. All natural foods contain certain amounts of phenylalanine. Therefore, once diagnosed, children should stop consuming natural diets and start treatment with a phenylalanine-restricted diet, including low-phenylalanine yogurt. Treatment should continue at least until the age of 12. When the concentration of blood phenylalanine is controlled at an ideal level, gradually add small amounts of natural food, adhering to the principle of low protein and low phenylalanine in the added foods.

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Written by Yan Xin Liang
Pediatrics
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Does phenylketonuria affect intelligence?

Phenylketonuria is a common amino acid metabolic disease, primarily caused by a deficiency of phenylalanine hydroxylase in the metabolic pathway of phenylalanine, preventing phenylalanine from converting into tyrosine. This leads to the accumulation of phenylalanine and its ketones in the body, which are then excreted in large amounts through urine. Its clinical manifestations are not uniform. The main clinical characteristic is intellectual disability, thus it does affect intelligence. Additionally, it can present various neuropsychiatric symptoms such as increased muscle tone, hyperreflexia, agitation, hyperactivity, convulsions, etc. It can also lead to reduced skin pigmentation and yellowing of hair among other symptoms. This disease can impact intelligence.

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Written by Yan Xin Liang
Pediatrics
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Do children with mild phenylketonuria need treatment?

Phenylketonuria is a common amino acid metabolic disease, primarily due to the deficiency of phenylalanine hydroxylase, preventing phenylalanine from being converted into tyrosine. This leads to the accumulation of phenylalanine and its keto acids in the body, which are then excreted in large amounts in the urine. It is a relatively common genetic amino acid metabolic disorder and is inherited as an autosomal recessive trait. Even in cases of mild symptoms, treatment is still required. The main treatment is a low-phenylalanine diet, which involves dietary control, as phenylalanine is an essential amino acid for protein synthesis. Special phenylalanine-formula milk powder is fed to infants, and at this stage, it is appropriate to add some complementary foods such as starchy vegetables and fruits, focusing on low-protein foods. The goal of dietary treatment is to maintain an appropriate concentration of phenylalanine in the blood.

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Written by Yan Xin Liang
Pediatrics
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Is phenylketonuria characterized only by pale facial skin?

Phenylketonuria is a common amino acid metabolic disorder. It is primarily due to the deficiency of phenylalanine hydroxylase, which prevents the conversion of phenylalanine to tyrosine, leading to a series of clinical symptoms. These can manifest as intellectual disability, neuropsychiatric symptoms, eczema, skin scratching, pigment loss, and a musty odor. The skin whiteness mentioned is not merely facial pallor; it affects the entire skin because the benefits of tyrosine are reduced, leading to decreased melanin synthesis. Consequently, the hair of affected children can also be lighter and tend to be brown.