Mechanism of phenylketonuria

Written by Hu Qi Feng
Pediatrics
Updated on September 03, 2024
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Phenylketonuria is characterized by reduced activity of phenylalanine hydroxylase, which fails to convert phenylalanine to tyrosine, causing extremely elevated levels of phenylalanine in the blood, cerebrospinal fluid, and tissues. This leads to the production of large amounts of phenylpyruvic acid, phenylacetic acid, phenyllactic acid, and p-hydroxyphenylacetic acid via alternative pathways. High concentrations of phenylalanine and its metabolic products can cause brain damage, which manifests as developmental intellectual disabilities, changes in skin and hair pigmentation, and a mousy urine odor, all part of a clinical syndrome.

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Written by Hu Qi Feng
Pediatrics
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Phenylketonuria lacks what enzyme?

Phenylketonuria is an autosomal recessive genetic disorder caused by a mutation in the phenylalanine hydroxylase gene, which leads to reduced enzyme activity and the accumulation of phenylalanine and its metabolites in the body, resulting in disease. Phenylketonuria is the most common congenital disorder of amino acid metabolism, clinically characterized by developmental delays in intelligence, light pigmentation of the skin and hair, and a mousey odor to the urine. It is often due to a deficiency of phenylalanine hydroxylase.

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Written by Hu Qi Feng
Pediatrics
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Mechanism of phenylketonuria

Phenylketonuria is characterized by reduced activity of phenylalanine hydroxylase, which fails to convert phenylalanine to tyrosine, causing extremely elevated levels of phenylalanine in the blood, cerebrospinal fluid, and tissues. This leads to the production of large amounts of phenylpyruvic acid, phenylacetic acid, phenyllactic acid, and p-hydroxyphenylacetic acid via alternative pathways. High concentrations of phenylalanine and its metabolic products can cause brain damage, which manifests as developmental intellectual disabilities, changes in skin and hair pigmentation, and a mousy urine odor, all part of a clinical syndrome.

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Written by Zeng Hai Jiang
Pediatrics
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Can patients with phenylketonuria eat fish and shrimp?

Children with phenylketonuria cannot eat fish and shrimp because phenylketonuria is caused by a deficiency of phenylalanine hydroxylase in the phenylalanine metabolic pathway, leading to metabolic disorder of phenylalanine in the liver. Phenylketonuria is the first hereditary metabolic disease that can be controlled by diet, as natural foods contain certain amounts of phenylalanine. Therefore, once diagnosed, children with phenylketonuria should stop consuming a natural diet and should be treated with a low phenylalanine diet. Fish and shrimp contain rich protein and high levels of phenylalanine, hence children with phenylketonuria cannot eat fish and shrimp.

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Written by Yao Li Qin
Pediatrics
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Phenylketonuria should be treated in which department?

Phenylketonuria is a common autosomal recessive genetic disorder due to a deficiency in the enzymes involved in the metabolic pathway of phenylalanine. It is a genetic metabolic disease. After the birth of a child, newborn screening is conducted for this disease. If a child is diagnosed with phenylketonuria or suspected of having the condition, it is common to visit a pediatric neurology department at a children's hospital. Phenylketonuria mainly causes varying degrees of intellectual disability, and some children may even experience epileptic seizures. Additionally, about 90% of affected children gradually develop lighter skin and hair, reduced iris pigmentation, dry skin, eczema, and a distinctive mouse-like urine odor, which is due to the excretion of phenylacetic acid in urine and sweat. It is a challenging genetic metabolic disorder to treat, requiring special dietary management. It is advisable to bring the child to the pediatric neurology department. Some hospitals may have a specialized department for genetic metabolic diseases. If such a department is available, it is recommended to consult there; otherwise, pediatric neurology is the appropriate alternative.

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Written by Hu Qi Feng
Pediatrics
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The pathogenesis of phenylketonuria

Phenylketonuria is an amino acid metabolic disease caused by a deficiency of phenylalanine hydroxylase. Phenylalanine is an essential amino acid for the human body, and it is partially converted into tyrosine by phenylalanine hydroxylase. Due to the reduced activity of phenylalanine hydroxylase, phenylalanine cannot be transformed into tyrosine. This leads to extremely high concentrations of phenylalanine in the blood, cerebrospinal fluid, and tissues. Through alternative metabolic pathways, large amounts of phenylpyruvic acid, phenylacetic acid, phenyllactic acid, and others are produced. High concentrations of phenylalanine and its metabolic products can cause brain damage.