- Main symptoms
- How the treatment is done
- Is phenylketonuria curable?
- How the diagnosis is made
- Because phenylalanine is toxic to phenylketonurics
Phenylketonuria is a rare genetic disease characterized by the presence of a mutation responsible for altering the function of an enzyme in the body responsible for the conversion of the amino acid phenylalanine into tyrosine, which leads to the accumulation of phenylalanine in the blood and which in high concentrations is toxic to the organism, which can cause intellectual disability and seizures, for example.
This genetic disease has an autosomal recessive character, that is, for the child to be born with this mutation, both parents must be at least carriers of the mutation. The diagnosis of phenylketonuria can be made right after birth by means of the heel prick test, and it is then possible to establish treatment early.
Phenylketonuria has no cure, however its treatment is done through food, and it is necessary to avoid the consumption of foods rich in phenylalanine, such as cheese and meat, for example.
Main symptoms
Newborns with phenylketonuria initially have no symptoms, but the symptoms appear a few months later, the main ones being:
- Skin wounds similar to eczema; Unpleasant odor, characteristic of the accumulation of phenylalanine in the blood; Nausea and vomiting; Aggressive behavior; Hyperactivity; Mental retardation, usually severe and irreversible; Convulsions; Behavioral and social problems.
These symptoms are usually controlled by an adequate diet and low in phenylalanine source foods. In addition, it is important that the person with phenylketonuria is monitored regularly by the pediatrician and nutritionist since breastfeeding so that there are no very serious complications and the child's development is not compromised.
How the treatment is done
The treatment of phenylketonuria has the main objective of decreasing the amount of phenylalanine in the blood. Therefore, the treatment usually indicated is the adoption of a diet low in foods containing phenylalanine, such as foods of animal origin, for example. Most of the foods that contain phenylalanine are also great sources of iron, so iron supplementation is usually indicated by a pediatrician or nutritionist. See which foods are high in phenylalanine.
It is important that the person is monitored for life and regularly to avoid complications, such as central nervous system involvement, for example. Find out how phenylketonuria is treated.
Women with phenylketonuria who want to become pregnant should have guidance from the obstetrician and nutritionist regarding the risks of increasing the concentration of phenylalanine in the blood. Therefore, it is important that it is evaluated by the doctor periodically, in addition to following a suitable diet for the disease and, probably, supplementing some nutrients so that both the mother and the child are healthy.
Is phenylketonuria curable?
Phenylketonuria has no cure and, therefore, treatment is done only with the control of food. The damage and intellectual impairment that can happen with the consumption of foods rich in phenylalanine is irreversible in people who do not have the enzyme or have the enzyme unstable or inefficient with regard to the conversion of phenylalanine to tyrosine. These damages, however, can be easily avoided through feeding.
How the diagnosis is made
The diagnosis of phenylketonuria is made shortly after birth by means of the heel prick test, which must be performed between the first 48 and 72 hours of the baby's life. This test is able to diagnose not only phenylketonuria in the baby, but also sickle cell anemia and cystic fibrosis, for example. Find out which diseases are identified by the heel prick test.
Children who have not been diagnosed through the heel prick test can be diagnosed by laboratory tests whose objective is to assess the amount of phenylalanine in the blood and, in the case of very high concentration, a genetic test can be performed to identify the disease-related mutation.
Through molecular tests it is possible to identify the effect of the mutation and, thus, determine the severity of the disease. Some mutations are capable of reducing or slowing down the activity of the enzyme, while others cause phenylalanine to no longer be recognized by the enzyme or make the enzyme very unstable, making normal function of its function difficult.
Identifying the type of mutation and the concentration of phenylalanine in the blood is very important for the doctor to check the degree of the disease and possible complications, in addition to assisting the nutritionist in the construction of the diet plan, which is always based on the amount of phenylalanine in the blood.. When the amount is low, the nutritionist can recommend the consumption of foods that contain little amount of phenylalanine in its composition and when the values of this amino acid are above the ideal, foods free of phenylalanine.
It is important that the dosage of phenylalanine in the blood is done regularly. In the case of babies it is important that it is done every week until the baby turns 1 year old, while for children between 2 and 6 years old the exam must be carried out fortnightly and for children from 7 years old, monthly. The early diagnosis of phenylketonuria allows the necessary care with food to be taken from the beginning, avoiding a series of undesirable consequences, such as permanent damage to the brain.
Because phenylalanine is toxic to phenylketonurics
Despite being present in several foods, phenylalanine needs to be converted into tyrosine, which is due to the action of an enzyme, phenylalanine hydroxylase, also called PAH.
In people with phenylketonuria, the PAH enzyme is produced defective due to genetic changes, which means that there is no conversion of phenylalanine into tyrosine and accumulation of phenylalanine in the blood. This amino acid can also be converted into pyruvic acid, making it very toxic to the body and can result in neuronal changes.
