When do people with phenylketonuria need to eat a special diet until?

Written by Zeng Hai Jiang

Pediatrics

Updated on January 07, 2025

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Phenylketonuria is the first genetic metabolic disease that can be treated through dietary control. Since natural foods contain certain amounts of phenylalanine, once children with phenylketonuria are diagnosed, they should stop consuming a natural diet and start a low-phenylalanine diet treatment. Treatment with a low-phenylalanine formula should continue at least until the age of 12. When the concentration of phenylalanine in the blood is controlled at an ideal level, gradually small amounts of natural diet can be reintroduced. The food added should adhere to the principles of being low in protein and phenylalanine.

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Written by Zeng Hai Jiang

Pediatrics

44sec

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Does phenylketonuria definitely cause intellectual disabilities when one grows up?

Phenylketonuria is a common amino acid metabolic disorder that is due to a deficiency of phenylalanine hydroxylase in the phenylalanine metabolic pathway, leading to metabolic disorder of phenylalanine in the liver. Phenylketonuria is the first genetic metabolic disorder that can be controlled and treated through diet. Once diagnosed, natural diet should be discontinued for the patient, and a low-phenylalanine diet should be administered. If phenylketonuria is diagnosed and treated early, intelligence can be normal. However, if not controlled, it can lead to delayed growth and development, especially in terms of intellectual development.

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Written by Yan Xin Liang

Pediatrics

1min 34sec

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The causes of phenylketonuria

Phenylketonuria is a common autosomal recessive genetic disorder, the most frequent primary clinical manifestation among congenital amino acid metabolic disorders. It is characterized by intellectual disability, pale skin and hair pigmentation, and a mouse urine-like odor. The main cause is that phenylalanine is an essential amino acid for the human body. The phenylalanine ingested is partly used for protein synthesis and partly converted to tyrosine by the action of phenylalanine hydroxylase, which is necessary for the synthesis of substances like adrenaline, melanin, and thyroxine. The disease is mainly due to a deficiency of phenylalanine hydroxylase, which inhibits the conversion of phenylalanine to tyrosine, resulting in increased concentrations of phenylalanine in the blood, cerebrospinal fluid, and various tissues. At the same time, due to the predominance of the main pathway, the enhancement of the secondary metabolic pathway leads to the deamination of phenylalanine by transaminase, producing a large amount of phenylpyruvic acid, which through oxidation produces a large amount of phenylacetic acid, phenyllactic acid, and p-hydroxyphenylpyruvic acid. These metabolic by-products are excreted in large quantities in the urine, and the high concentrations of phenylalanine and its by-products accumulate extensively in brain tissue, thereby causing damage to brain cells.

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Written by Yan Xin Liang

Pediatrics

38sec

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Is the incidence of phenylketonuria high?

Phenylketonuria is an autosomal recessive hereditary disease and is the most common congenital amino acid metabolic disorder. The main clinical manifestations include distinctive features such as intellectual disability, light skin and hair pigmentation, and a mouse-like urine odor, which is named after the large amounts of phenylketone acid metabolites excreted in the urine. The incidence of this disease varies by race and region, and the overall incidence in China is approximately 1:11,000, meaning one in eleven thousand. The incidence is higher in the northern population than in the southern population, though it is not particularly high.

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Written by Zeng Hai Jiang

Pediatrics

47sec

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How to determine if phenylketonuria is mild

Phenylketonuria severity is generally determined by clinical manifestations and blood phenylalanine concentration. Mild phenylketonuria is characterized by mild or asymptomatic intelligence, motor, and developmental delays, light hair and skin color, and a musty odor in urine and sweat. It includes clinical features such as seizures accompanied by abnormal mental and behavioral symptoms, with blood phenylalanine levels less than 120 to 360 micromoles per liter. This is primarily seen in a very small number of newborns or premature infants, or in cases where there is higher residual activity of phenylalanine hydroxylase enzyme.

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Written by Yan Xin Liang

Pediatrics

41sec

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Why does phenylketonuria lead to intellectual disability?

Phenylketonuria is a common amino acid metabolic disease, mainly due to the deficiency of phenylalanine hydroxylase, which prevents phenylalanine from being transformed into tyrosine, leading to the accumulation of phenylalanine and its keto acids. Due to the lack of tyrosine in the body, it affects the growth and development of the brain, resulting in intellectual developmental delays. Therefore, children with phenylketonuria often exhibit intellectual disabilities, as well as some psychiatric and neurological symptoms, such as increased muscle tone, restlessness, hyperactivity, abnormal behavior, and heightened excitability.