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Phenylketonuria
Can phenylketonuria be prevented?
Phenylketonuria belongs to a recessive hereditary metabolic disease; how can we take preventive measures? First, we must avoid consanguineous marriages. Second, we need to conduct newborn screening to achieve early diagnosis, early detection, and early treatment. Third, for pregnant women with a family history of this disease, it is mandatory to use DNA analysis or methods like amniotic fluid testing for prenatal diagnosis of their fetuses. Prevention is better than cure. By taking preventive measures early, the chances of complications occurring are greatly reduced. If a baby shows symptoms of newborn phenylketonuria, parents should not take it lightly and should actively cooperate with the treatment.
Does phenylketonuria definitely cause intellectual disabilities when one grows up?
Phenylketonuria is a common amino acid metabolic disorder that is due to a deficiency of phenylalanine hydroxylase in the phenylalanine metabolic pathway, leading to metabolic disorder of phenylalanine in the liver. Phenylketonuria is the first genetic metabolic disorder that can be controlled and treated through diet. Once diagnosed, natural diet should be discontinued for the patient, and a low-phenylalanine diet should be administered. If phenylketonuria is diagnosed and treated early, intelligence can be normal. However, if not controlled, it can lead to delayed growth and development, especially in terms of intellectual development.
Does phenylketonuria have a distinctive facial appearance?
Phenylketonuria is characterized by a specific facial appearance, primarily presenting with pale skin and yellow hair. Some affected children may develop eczema due to a disruption in melanin synthesis, which results in a distinctive skin color. Additionally, there are neuropsychiatric abnormalities, such as intellectual disability, increased excitability, and heightened muscle tone. The urine of patients has a plastic-like smell, largely because phenylketonuria is a hereditary metabolic disease. Newborns exhibit hyperphenylalaninemia, but as harmful metabolites of phenylalanine are not present in high concentrations before feeding begins, initial conditions at birth are often normal. However, as diet is introduced and metabolite concentrations increase, specific clinical symptoms, including severe cases of epileptic seizures manifested as infantile spasms, nodding seizures, or other forms, become evident. Therefore, dietary management is essential in treatment.
If phenylketonuria is not treated, what will happen?
Phenylketonuria (PKU) is an amino acid metabolic disorder primarily caused by a deficiency in phenylalanine hydroxylase. This deficiency prevents phenylalanine from being converted to tyrosine, leading to a significant accumulation of phenylalanine, which is then excreted in large quantities in the urine. It is a common genetic metabolic disorder. If not treated, it can lead to developmental delays in children, particularly in intellectual development, with markedly lower IQ than peers, especially noticeable in language development disorders. Additionally, it can also present with neurological and psychiatric symptoms such as agitation, hyperactivity, increased muscle tone, and hyperreflexia. There is also depigmentation of the skin and hair, and the urine may have a mousy odor.
Phenylketonuria patients lack phenylalanine hydroxylase.
Phenylketonuria is an autosomal recessive genetic disorder caused by mutations in the phenylalanine hydroxylase gene, leading to reduced enzyme activity and resulting in the accumulation of phenylalanine and its metabolic products in the body, causing the disease. Phenylketonuria is the most common congenital amino acid metabolism disorder, clinically presenting with intellectual developmental delays, lighter skin and hair pigmentation, and a musty urine odor. The disease is mainly caused by mutations in the phenylalanine hydroxylase gene, leading to reduced enzyme activity.
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.
Phenylketonuria treatment duration before discontinuation
Phenylketonuria is the first genetic metabolic disease that can be treated through dietary control. Once diagnosed with phenylketonuria, active treatment must be given, ceasing a natural diet and implementing a low-phenylalanine diet. Generally, a low-phenylalanine milk formula should be administered at least until the age of three. When the concentration of phenylalanine in the blood is adjusted to an ideal range, a small amount of natural diet can gradually be reintroduced. The reintroduced diet should still adhere to low-protein and low-phenylalanine standards.
Is phenylketonuria often misdiagnosed?
Phenylketonuria belongs to congenital hereditary metabolic disorders and is caused by enzyme deficiencies in the phenylalanine metabolic pathway. Misdiagnosis of phenylketonuria is not common; if the disease develops, meaning that the child has typical clinical manifestations, it is relatively easy to diagnose. However, once a child exhibits the typical clinical manifestations of phenylketonuria such as blood phenylalanine levels, by the time of diagnosis the child may already have varying degrees of neurological damage, meaning the child might already have intellectual disabilities. Therefore, in such cases, we cannot rely solely on clinical symptoms for diagnosis but should instead carry out newborn disease screening promptly after birth. By diagnosing and treating before any clinical symptoms appear, we can prevent the occurrence of neurological complications, allowing the child to grow and develop like a normal child.
What can be eaten with phenylketonuria?
Phenylketonuria is primarily due to a deficiency of phenylalanine hydroxylase in the body, which prevents the conversion of phenylalanine to tyrosine. Due to the blockage of the metabolic pathway, secondary metabolic pathways are enhanced, leading to the deamination of phenylalanine and the production of large amounts of phenylpyruvic acid. Through oxidation, by-products such as phenylacetic acid, phenyllactic acid, and para-hydroxyphenylpyruvic acid are formed. The treatment mainly involves the use of low-phenylalanine formula milk. When the concentration in the blood reaches the desired level, natural foods can be gradually added in small amounts. Breast milk is the preferred choice as it contains only one-third of the phenylalanine content of cow's milk. For older infants and children, cow's milk, porridge, noodles, and eggs can be added. The principle for introducing foods should be based on low protein and low phenylalanine content, adjusted according to the phenylalanine concentration in the blood. Both too high and too low levels of phenylalanine can affect growth and development.
Is phenylketonuria characterized only by pale facial skin?
Phenylketonuria is a common amino acid metabolic disorder. It is primarily due to the deficiency of phenylalanine hydroxylase, which prevents the conversion of phenylalanine to tyrosine, leading to a series of clinical symptoms. These can manifest as intellectual disability, neuropsychiatric symptoms, eczema, skin scratching, pigment loss, and a musty odor. The skin whiteness mentioned is not merely facial pallor; it affects the entire skin because the benefits of tyrosine are reduced, leading to decreased melanin synthesis. Consequently, the hair of affected children can also be lighter and tend to be brown.