Phenylketonuria is a common amino acid metabolic disorder caused by an enzyme defect in the phenylalanine metabolic pathway that prevents the conversion of phenylalanine to tyrosine, resulting in the accumulation of phenylalanine and its keto acids and their massive excretion in the urine. The disease is relatively common among inherited amino acid metabolism deficiency diseases, and its mode of inheritance is autosomal recessive. Symptoms are as follows: 1. Normal at birth: symptoms usually appear at 3-6 months of age and become apparent at 1 year of age.
2. Neurological system: The main cause is a lag in intellectual development, with varying degrees of intellectual decline. Seizures may also occur, which may decrease or stop with age. It may be accompanied by dull expression, abnormal behavior, hyperactivity, muscle spasm and increased muscle tone.
3. Appearance changes: The skin is often dry and prone to eczema and skin scratching. At birth, the hair color is normal, but in the postnatal months, due to the inhibition of tyrosinase, the melanin synthesis is reduced, so the child’s hair color is light and brown.
4. Urine and sweat abnormalities: Due to the lack of phenylalanine hydroxylase, phenylalanine produces phenyl lactate and phenylacetic acid from another pathway, which is excreted from sweat and urine, and has a musty odor (or rat odor).
In conclusion, the main clinical features of children with phenylketonuria are mental retardation, psychoneurological symptoms, eczema, skin scratching signs and depigmentation and rat odor, and EEG abnormalities. If early diagnosis and early treatment are obtained, the aforementioned clinical manifestations may not occur, intelligence may be normalized, and EEG abnormalities may be restored.