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Phenylketonuria
What is the probability of phenylketonuria?
Phenylketonuria is an autosomal recessive genetic disorder primarily caused by mutations in the phenylalanine hydroxylase gene, leading to reduced enzyme activity and the accumulation of phenylalanine and its metabolites in the body, resulting in the disease. Phenylketonuria is the most common congenital amino acid metabolism disorder, with clinical manifestations mainly including intellectual developmental delays, light skin and hair pigmentation, and a mouse urine odor. The incidence of the disease varies by race and region. In China, the incidence of phenylketonuria is approximately 1 in 11,000, meaning that about one in 11,000 children suffers from phenylketonuria.
Can phenylketonuria be treated?
Can phenylketonuria be treated? Yes, it can be treated, and treatment should begin immediately once diagnosed. The younger the age at which treatment begins, the better the prognosis. Infants are generally treated with low-phenylalanine formula milk. Once the blood phenylalanine concentration drops to an ideal level, natural foods can gradually be added in small amounts, with a preference for adding breast milk, since it contains only one-third the phenylalanine content of cow's milk. Older infants and children can add foods like milk, porridge, noodles, and eggs. Added foods should follow the principle of being low in protein and phenylalanine. The amount and frequency of these foods should be determined based on the blood phenylalanine concentration. Concentrations that are too high or too low can affect the growth and development of the child. As each child's tolerance to phenylalanine concentration differs, it is necessary to regularly measure the blood phenylalanine concentration during dietary treatment and adjust the diet according to the specific situation of the child, avoiding increased phenylalanine levels or deficiency.
How is phenylketonuria diagnosed?
Phenylketonuria screening is routinely conducted in China for all newborns. This involves pricking the heel to collect peripheral blood, which is then dropped on specialized filter paper and dried. The samples are sent to a screening laboratory for the measurement of phenylalanine concentration. If the concentration exceeds the threshold, further testing for phenylalanine is conducted. Normally, the concentration should be less than 120 micromoles per liter. Additionally, an analysis of the urinary purine profile can be performed.
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.
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.
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.
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.