Phenylketonuria (PKU) is an inherited disease that affects the brain due to the increased density of a substance called "phenylalanine" in the blood. "Phenylalanine" is one of the building blocks of proteins, which are indispensable elements of our diet. It is found in most of the foods and some artificial sweeteners. The proteins taken into the body through the foods we eat daily are digested in the body. Proteins are broken down into “amino acids”, smaller units that make up itself during digestion. Then it is absorbed in the small intestine and enters the blood. It is transported to the liver through blood. A number of enzymes are secreted in the liver. One of these enzymes, "Phenylalanine Hydroxylase (FAH), converts the amino acid" phenylalanine "to another amino acid called" tyrosine. The amino acid "tyrosine" is essential for many functions in the body. Protein synthesis is used in many events, such as the production of many hormones that is necessary for the body. A number of "genes" in the liver cells are responsible for the production of this enzyme that converts the "phenylalanine" amino acid in the liver. These genes are defective due to an innate error in PKU patients. Therefore, these enzymes secreted from the liver are either not produced at all or are produced incorrectly. As a result, the amino acid "phenylalanine" transported to the liver cannot be converted. As it cannot be converted, its density in the blood begins to increase. Blood rich in phenylalanine reaches the brain through circulation. Brain cells are very sensitive to these amino acids. Therefore, they begin to create permanent damage to the brain. The faulty genes mentioned are transferred from mother and father to the child. Defective production of the enzyme results from transferring the faulty gene from both mother and father.
What are the Symptomes and Types of PKU?
There are several types of PKU disease. In some types, it is not able to perform the enzyme function since the substances necessary for the enzyme to work are not found in the body. Findings can be alleviated by giving these items from outside. PKU symptoms and septomes range from mild to severe. Its most severe form is known as the classic PKU. In these individuals, the activity of “FAH” enzyme is very low or completely disappeared. Babies with classic PKU have a normal appearance for up to several months. If it does not be treated, permanent mental disability develops. In less severe forms of PKU, the activity of "FAH" enzyme has not completely disappeared, it continues some functions. Therefore, the level of phenylalanine does not rise much. This causes a reduced risk of brain damage.
How is it diagnosed?
A blood sample is taken from the baby's heel no later than 24 hours after birth. It is tested for other rare conditions, including Phenylketonuria (PKU), which can damage the baby's growing brain. The level of "phenylalanine" in the baby's blood is checked with the test. High levels of phenylalanine does not necessarily mean PKU. It requires more tests to be sure.
What is the Treatment?
Limited lifetime dietary treatment from the amino acid "phenylalanine" is required. Thus, the amount of “phenylalanine” taken with foods is restricted and its level in the blood is prevented from increasing. Phenylalanine is the building block of many proteins. Therefore, the diet restricted from phenylalanine is synonymous with the restricted diet from protein. Containing high protein; milk and its products, foods such as eggs and fish are completely prohibited. Vegetables and fruits can be included in a limited diet. In addition, low-protein baked goods, chocolate and substitute foods can be included in the diet in a limited amount. The amount of protein and phenylalanine to be taken daily depends on the patient's tolerance of phenylalanine and is determined by the doctor's control after the tests. Dietician physician determines the patient's diet program so as not to exceed these determined protein and phenylalanine values and at the same time to ensure that the patient lives healthy. In addition, formula foods are used in order for the patient to receive other amino acids necessary for his life. Lifelong doctor control is provided by measuring the patient's blood phenylalanine levels in certain periods.
When Should Treatment Be Started?
In order for the findings not to develop, ideally, it is necessary to start diet therapy within 1 week or 10 days from birth. If the diet is not followed, the decline in intelligence becomes evident in the 5th and 6th months after birth. Starting diet as early as possible is crucial to prevent damage. If the diet is followed, the destruction in the body can be stopped and the patients can develop their life mentally and continue to their life.
Gülşah Kurtoğlu
Food Engineer