The pathogenesis of phenylketonuria

Written by Hu Qi Feng

Pediatrics

Updated on September 02, 2024

00:00

00:00

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.

Other Voices

home-news-image

Written by Zeng Hai Jiang

Pediatrics

48sec

home-news-image

Can people with phenylketonuria not eat things high in protein?

Phenylketonuria patients should avoid foods high in protein, as phenylketonuria is a common amino acid metabolism disorder caused by a deficiency of phenylalanine hydroxylase in the metabolic pathway of phenylalanine, leading to disordered metabolism of phenylalanine in the liver. Phenylketonuria is a hereditary metabolic disease that can be managed through diet. Natural foods contain certain amounts of phenylalanine. Once diagnosed, the patient should cease consuming natural diets and switch to a phenylalanine-restricted diet. Foods rich in protein have higher amounts of phenylalanine, thus, those with phenylketonuria should not consume foods high in protein.

home-news-image

Written by Zeng Hai Jiang

Pediatrics

41sec

home-news-image

How long does it take for phenylketonuria to manifest?

Phenylketonuria is a common amino acid metabolic disease. Most infants appear normal at birth and do not show any specific clinical symptoms during the neonatal period, although some newborns may experience symptoms such as feeding difficulties, vomiting, or irritability. Symptoms of phenylketonuria gradually appear in the first three months after birth, including changes such as hair turning from black to yellow, skin whitening, delayed growth and intellectual development, seizures, hyperactive reflexes, eczema, etc. The sweat and urine of affected children will have a mouse-like odor.

home-news-image

Written by Yan Xin Liang

Pediatrics

1min 2sec

home-news-image

Causes of Phenylketonuria

The cause of phenylketonuria is that phenylalanine is an essential amino acid for the human body. Some of the phenylalanine ingested is used for protein synthesis, while another part is converted into tyrosine by the action of phenylalanine hydroxylase. Only a small amount of phenylalanine undergoes a secondary metabolic pathway and is converted into phenylpyruvate under the action of transaminase. Due to the reduced activity of phenylalanine hydroxylase in affected children, phenylalanine cannot be converted into tyrosine, leading to an extremely high concentration of phenylalanine in blood, cerebrospinal fluid, and tissues. This, through a bypass metabolic pathway, results in the production of a large amount of phenylpyruvate, phenylacetate, phenyllactate, and p-hydroxyphenylacetate. The high concentration of phenylalanine and its metabolic products then leads to brain damage, which is the cause of the disease.

home-news-image

Written by Yan Xin Liang

Pediatrics

50sec

home-news-image

Phenylketonuria smells like mouse urine.

Phenylketonuria is a common amino acid metabolic disorder primarily caused by a deficiency of phenylalanine hydroxylase. This deficiency prevents phenylalanine from being converted to tyrosine, leading to the accumulation of phenylalanine and ketone bodies, which are then excreted in large amounts in the urine. This disease is relatively common among genetic amino acid metabolic disorders and is inherited as an autosomal recessive trait. Additionally, due to the lack of phenylalanine hydroxylase, phenylalanine is metabolized through another pathway, resulting in increased production of phenyllactic acid and phenylacetic acid, which are excreted through sweat and urine, giving off a mouse-like urine odor.

home-news-image

Written by Quan Xiang Mei

Pediatrics

1min 2sec

home-news-image

Does phenylketonuria cause liver dysfunction?

Phenylketonuria generally does not cause abnormalities in liver function. Phenylketonuria is a common amino acid metabolic disorder, mainly due to a deficiency of an enzyme in the phenylalanine metabolic pathway, preventing phenylalanine from being converted into tyrosine. This leads to the accumulation of phenylalanine and its keto acids, which are then excreted in large amounts in the urine. This disease is a relatively common genetic amino acid metabolic defect. Once diagnosed with phenylketonuria, the main treatment is a dietary therapy, which includes a low-phenylalanine diet. It is important during the upbringing of children to ensure that the child's living environment is quiet and comfortable. Therefore, in terms of prevention of the disease, it is important to avoid consanguineous marriage, conduct newborn screening, and focus on early detection and early treatment.