Phenylketonuria is a disease.

Written by Yan Xin Liang
Pediatrics
Updated on September 02, 2024
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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 Yan Xin Liang
Pediatrics
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Can phenylketonuria be cured?

Phenylketonuria is one of the few treatable genetic metabolic diseases. It strives for early diagnosis and treatment to avoid irreversible damage to the nervous system. Once diagnosed, aggressive treatment should be given. The younger the age at which treatment starts, the better the effect. The main approach is to use a low-phenylalanine formula milk. When the blood concentration drops to a normal level, natural diet can gradually be added in small amounts, with breast milk being the preferred choice, as it contains only one-third the phenylalanine of cow's milk. Larger infants can add cow's milk, porridge, noodles, eggs, etc. The added foods should also follow the principle of being low in protein and low in phenylalanine, because concentrations of phenylalanine that are too high or too low will affect growth and development. Low-phenylalanine treatment should continue at least until after puberty. Lifelong treatment is more beneficial for patients. This disease can only control symptoms, and lifelong treatment is the best; it cannot be completely cured.

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Written by Yan Xin Liang
Pediatrics
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Does phenylketonuria affect intelligence?

Phenylketonuria is a common amino acid metabolic disease, primarily caused by a deficiency of phenylalanine hydroxylase in the metabolic pathway of phenylalanine, preventing phenylalanine from converting into tyrosine. This leads to the accumulation of phenylalanine and its ketones in the body, which are then excreted in large amounts through urine. Its clinical manifestations are not uniform. The main clinical characteristic is intellectual disability, thus it does affect intelligence. Additionally, it can present various neuropsychiatric symptoms such as increased muscle tone, hyperreflexia, agitation, hyperactivity, convulsions, etc. It can also lead to reduced skin pigmentation and yellowing of hair among other symptoms. This disease can impact intelligence.

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Written by Zeng Hai Jiang
Pediatrics
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Can phenylketonuria eat corn?

People with phenylketonuria can eat corn. Phenylketonuria is a hereditary metabolic disease that can be treated through dietary control. Once diagnosed with phenylketonuria, one must stop a natural diet and switch to a low-phenylalanine diet. When the concentration of phenylalanine in the blood drops to an ideal level, natural foods can be gradually reintroduced in small amounts, but the diet must still adhere to low-protein and low-phenylalanine standards. Corn mainly consists of starch and does not contain phenylalanine, so individuals with phenylketonuria can eat corn.

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Written by Quan Xiang Mei
Pediatrics
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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.

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Written by Hu Qi Feng
Pediatrics
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Phenylketonuria Clinical Symptoms

Phenylketonuria may appear normal at birth, but symptoms usually start to appear between three to six months, with the symptoms becoming most evident at one year old. These are often manifestations of the nervous system, with prominent developmental delays in intelligence. The IQ is often lower than normal, and there may be abnormal behaviors, minor epileptic seizures, and, in a few children, increased muscle tone and hyperactive tendon reflexes. Due to insufficient melanin synthesis a few months after birth, affected children’s hair color changes from black to yellow, their skin is fair, and skin eczema is relatively common. Due to the elevated excretion of phenylacetic acid in urine and sweat, there is a distinct mouse-like urine smell.