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How is phenylketonuria inherited?


Phenylketonuria in children is a common autosomal recessive disorder caused by an enzyme defect in the phenylalanine metabolism pathway. Both parents have chromosomal defects but are asymptomatic, and children of consanguineous marriages have a high incidence. At birth, the child is normal. After breastfeeding, symptoms generally appear within 3-6 months, and symptoms are obvious at 1 year old. The disease has become one of the routine newborn screening programs in obstetrics.

In summary, phenylketonuria is an autosomal recessive inheritance. The mutated gene is located on the long arm of chromosome 12 (12q24.1). Small variations in this gene may cause the disease, not due to genetic deletions. It is a genetic disorder caused by two heterozygous marriages and is common in consanguineous marriages, affecting about 40 percent of sibling children. So far, more than 400 pAH gene mutations have been found, including deletions, missense mutations, nonsense mutations, synonymous mutations, etc. More than 70 genetic mutations have been reported in the Chinese.

What is phenylketonuria?

Phenylketonuria is a common amino acid metabolism disorder. Due to an enzymatic defect in the phenylalanine metabolic pathway, phenylalanine cannot be converted to tyrosine, resulting in the accumulation and excretion of phenylalanine and its ketoacids in the urine. Clinical manifestations are mental retardation, convulsions and hypopigmentation. The disease is autosomal recessive inheritance.

Phenylketonuria is a congenital metabolic disease. Deficiency of phenylalanine hydroxylase (pAH) in the liver due to chromosomal gene mutation leads to disturbance of phenylalanine (pA) metabolism and central nervous system damage. Rare signs of neurological abnormalities include microcephaly, increased muscle tone, abnormal gait, tendon hyperreflexia, mild tremors in the hands, and repetitive limb movements. Due to a lack of melanin, children often have yellow hair, light skin, and irises. Unpleasant rat urine smell in children's urine. At the same time, children are prone to eczema, vomiting, diarrhea, etc. A low-phenylalanine diet is the only way to treat classic pKU. The goal of treatment is to prevent brain damage what is pku.

Who is susceptible to phenylketonuria.

The main hazard is brain damage. The child was born with no abnormalities. Without special dietary treatment, symptoms usually begin to appear at 3 to 6 months, with the most obvious symptoms appearing at 1 year of age. This disease is mainly mental retardation, and may have symptoms such as abnormal behavior, convulsions, and increased muscle tension, eventually leading to moderate mental retardation and becoming a heavy burden on the family and society. Insufficient synthesis of melanin due to abnormal metabolism of phenylalanine, yellowing of hair, lightening of skin and iris in children. There is often a very unpleasant smell of rat urine due to the abnormal metabolites accumulated in the blood being excreted through the urine. In addition, children are often accompanied by eczema, vomiting and so on.

Phenylketonuria is not unusual in newborns and early infancy, and symptoms appear gradually with growth and development. Therefore, the disease lies in early detection and treatment to avoid irreversible neurological damage. Treated with good results within 3 months of birth. The disorder can be detected and diagnosed early with newborn screening.

The most important treatment for this disease is diet therapy. Human milk, animal milk and common foods are high in phenylalanine and are not suitable for feeding children. Special low phenylalanine milk powder should be used. The foods to be added in the future should be mainly low-protein foods such as starch, vegetables and fruits, and the serum phenylalanine concentration should always be kept at a normal level to avoid brain damage and normal intellectual development. Diet therapy should continue at least until puberty. Dietary treatment for this disorder is expensive, so it is best to prevent and avoid consanguineous marriages.