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Phenylketonuria
What foods should children with phenylketonuria eat?
Phenylketonuria is a common amino acid metabolic disorder, an autosomal recessive genetic disease, and a type of hereditary metabolic disease that can be treated through dietary control. All natural foods contain certain amounts of phenylalanine. Therefore, once diagnosed, children should stop consuming natural diets and start treatment with a phenylalanine-restricted diet, including low-phenylalanine yogurt. Treatment should continue at least until the age of 12. When the concentration of blood phenylalanine is controlled at an ideal level, gradually add small amounts of natural food, adhering to the principle of low protein and low phenylalanine in the added foods.
Does phenylketonuria require a lifetime of special milk consumption?
Phenylketonuria does not require a lifetime of special milk consumption. It is the first genetically inherited metabolic disorder that can be treated through dietary control. Once diagnosed with phenylketonuria, one must stop a natural diet and begin treatment with a low-phenylalanine diet. The low-phenylalanine milk formula should be consumed at least until the age of 12. When the concentration of phenylalanine in the blood is controlled within the ideal range, it is possible to appropriately add a small amount of natural diet, adhering to principles of low protein and low phenylalanine.
Can phenylketonuria cause hair to turn white?
Phenylketonuria is caused by a mutation in the phenylalanine hydroxylase gene, resulting in reduced or lost enzyme activity, and a metabolic disorder of phenylalanine in the liver. Children with phenylketonuria lack phenylalanine hydroxylase, leading to reduced tyrosine and normal metabolic products. The content of phenylalanine in the blood increases, secondary metabolic pathways are enhanced, producing phenylpyruvic acid, phenylacetic acid, and phenyllactic acid, which are excreted in large amounts in the urine. High concentrations of phenylalanine and its abnormal metabolic products inhibit tyrosinase, leading to disturbances in melanin synthesis. Therefore, untreated children will gradually show changes in hair color from black to yellow and skin lightening after three months.
What is the normal value for phenylketonuria?
Phenylketonuria is a common autosomal recessive genetic disorder and the most common congenital amino acid metabolism disorder. It primarily manifests as intellectual disability, light skin and hair pigmentation, and a mousey urine odor. Newborn screening includes routine screening for phenylketonuria as it is a treatable hereditary metabolic disorder, emphasizing the importance of early diagnosis and treatment. Nowadays, newborn screening systems are widely implemented. Generally, this involves collecting a blood sample through a heel prick, dropping the blood on specialized filter paper, and then air drying before sending it to a screening laboratory to measure the phenylalanine concentration. Typically, a normal concentration should be less than 120 micromoles per liter. If the phenylalanine concentration exceeds 1200 micromoles per liter, it can be diagnosed as classical phenylketonuria.
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.
Early symptoms of phenylketonuria
Phenylketonuria is a hereditary metabolic disease caused by a deficiency or low activity of phenylalanine hydroxylase. Its main clinical manifestations include very obvious developmental delays in children and significantly lower IQ than their peers, severely affecting the child's growth and development. Due to the lack of this enzyme, the increase of abnormal metabolic products affects brain function, leading to symptoms such as seizures, convulsions, increased muscle tone, as well as hyperactivity and restlessness in children. The skin becomes particularly dry, prone to eczema, appears pale, and the hair turns yellow. The urine has a distinct mouse-like odor. Once diagnosed, early treatment is essential to reduce the sequelae of brain damage. The earlier the treatment, the better the prognosis. For these children, a special formula is needed, which is low in phenylalanine.
Can phenylketonuria be treated with surgery?
Phenylketonuria (PKU) in children cannot be treated surgically. PKU is an autosomal recessive genetic disorder caused by a deficiency in the enzyme needed for the metabolic pathway of phenylalanine. Typically, there are no obvious symptoms in newborns, although some children may experience non-specific symptoms such as vomiting and feeding difficulties. If no relevant treatment is pursued, the child may gradually show signs of developmental delays in movement and intellect, and the hair might change from black to yellow while the skin tends to be paler. As the child grows older, the intellectual delays become more pronounced, and in severe cases, they might develop cerebral palsy. This disease can be treated in its early stages through dietary methods, and the younger the age at which treatment begins, the better the outcomes.
Does phenylketonuria require chromosome testing?
Phenylketonuria is usually screened during the neonatal period through routine blood testing, where the level of phenylalanine in the blood is measured to screen each newborn. This enables early diagnosis and treatment, hence reducing the occurrence of intellectual disabilities. Phenylketonuria can also be screened prenatally before the birth of the newborn. It is an autosomal recessive genetic disorder, closely related to chromosomal abnormalities. Therefore, prenatal screening can be conducted by amniocentesis between the 16th to 20th weeks of pregnancy. Chromosomal abnormalities detected through the amniocentesis indicate that the fetus carries the pathogenic gene, meaning the child will be born with phenylketonuria. If both parents carry related genes, it is crucial to undergo prenatal screening and chromosomal analysis to eliminate the risk of the fetus developing the condition.
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.
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.