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 Yan Xin Liang
Pediatrics
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How is phenylketonuria diagnosed?

How is phenylketonuria diagnosed? Firstly, we start with screening, which is usually done when the newborn is 3 to 7 days old by heel prick to collect peripheral blood, which is then dropped onto specialized filter paper for the determination of phenylalanine concentration. If the concentration of phenylalanine is above the cutoff value, further determination of phenylalanine concentration is conducted. The normal concentration is less than 120 umol/L. If the concentration of phenylalanine is greater than 1200 umol/L, it suggests severe phenylketonuria. Moderate levels are above 360 umol/L, and mild levels are above 120 umol/L but less than 360 umol/L. Furthermore, diagnosis can be confirmed through DNA analysis, currently available tests include screening for mutations in the phenylalanine hydroxylase gene.

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Written by Yan Xin Liang
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Phenylketonuria is a disease.

Phenylketonuria is an autosomal recessive genetic disorder resulting from mutations in the phenylalanine hydroxylase gene, leading to reduced enzyme activity and the accumulation of phenylalanine and its metabolic products in the body, thereby causing this disease. Phenylketonuria is the most common congenital amino acid metabolic disorder, clinically characterized by intellectual developmental delays, light skin and hair pigmentation, and a mouse-like urine odor. The incidence of the disease varies by race and region, with an incidence rate in China of about 1 in 11,000. Phenylalanine is an essential amino acid for the human body, but due to reduced activity of phenylalanine hydroxylase, phenylalanine cannot be converted into tyrosine, leading to extremely high concentrations of phenylalanine in the blood, cerebrospinal fluid, and tissues. Abnormal metabolism produces a large amount of phenylpyruvic acid, phenylacetic acid, phenyllactic acid, and p-hydroxyphenylacetic acid, along with high concentrations of phenylalanine and its metabolic products, causing brain damage and corresponding symptoms.

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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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home-news-image
Written by Hu Qi Feng
Pediatrics
40sec home-news-image

Phenylketonuria inheritance mode

Phenylketonuria is an autosomal recessive genetic disorder, caused by a mutation in the phenylalanine hydroxylase gene leading to reduced enzyme activity. This results in the accumulation of phenylalanine and its metabolic products in the body, causing the disease. It is the most common congenital amino acid metabolism disorder and is clinically characterized by delayed intellectual development, changes in skin and hair pigmentation, and a mousy urine odor. The incidence of this disease in China is approximately 1 in 11,000, and it is inherited in an autosomal recessive manner.