Phenylketonuria: Symptoms and Treatment

Phenylketonuria is a fairly serious hereditary disease, the main severity of which is concentrated primarily on the nervous system. Phenylketonuria, the symptoms of which are most often found among girls, arises from the disturbance of amino acid metabolism, while taking into account the CNS’s lesion, its manifestations are reduced to a disruption of mental development.



General Description

In its classical form, which is relevant for most cases, phenylketonuria, which is also commonly referred to as phenylpyruvic oligophrenia, is associated with a sharp decrease in the activity of the hepatic enzyme. In particular, it is phenylanin-4-hydroxylase. The normal state of the body involves the catalysis of its conversion into tyrosine phenylalanine. 1% of cases is marked by the appearance of an atypical form of phenylketonuria, which arises due to mutations in other types of genes that are responsible for the process of encoding the enzymes. The inheritance of the disease occurs in accordance with the autosomal recessive scheme.

With regard to the processes occurring in the disease under consideration, they are as follows. The emergence of a characteristic metabolic block provokes the activation of side pathways by the exchange of phenylalanine, which leads to the accumulation of toxic derivatives from its action. Such derivatives include, in particular, phenyl-milk and phenylpyruvic acids, practically not formed in the normal state of the organism. They also affect the central nervous system, provoking violations of protein metabolism, the exchange of lipoproteins and the exchange of glycoproteins. At the same time, there are disorders in the transport of amino acids, disorders in the exchange of serotonin and catecholamines, and perinatal factors also become relevant.

In addition to this, the practically absent orthophenyl acetate and phenylethylamine also begin to form. Their excess provokes disturbances in the metabolism of lipids that occurs in the brain. This is supposed to be the reason for the progressive state of decline in the intellect in patients with this disease, which can even achieve idiocy. In general, finally, the mechanism, in accordance with the action of which there is a disruption in the development of brain functions in the case of an actual disease of the body for phenylketonuria, is not clear.

Phenylketonuria: Symptoms of Disease

Here, first of all, it is important to note that the first weeks of a child’s life are not allowed to outwardly identify the disease. The first signs of it appear after two to six months from the birth of the baby. He becomes sluggish, there is a lack of interest in the conditions surrounding him and the world as a whole. Also, the child becomes restless, muscle tone is disturbed. There is vomiting, convulsions, severe skin eczema. Eczema in particular means an acute or chronic form of an inflammatory and non-contagious disease in which a rash is formed. The nature of the disease is allergic, additional symptoms of symptoms are burning sensation and severe itching of the skin. The tendency to relapse, that is, to the re-occurrence of symptoms after a relative temporary calm, is also relevant.

The sixth month allows you to determine the lag in the development of the child. At the same time, the ability to focus on individual subjects is lost, the kid ceases to recognize his parents. There is no reaction to colored / bright toys. It is important to proceed promptly to treatment, otherwise the backwardness of development will be gradually progressed only in the actual processes for it.

The physical development of sick infants at the physical level is marked by less disturbances than on the psychic. In the girth, the head may be somewhat smaller than it is for the norm indicators. Zubki erupt later, later the child begins to sit and walk. Adoption of the standing position in such children is associated with a wide separation for this leg, as well as with bending them in the knees and hips, the shoulders and head are omitted. As for the peculiarities of walking in sick children, it is characterized by rocking, small steps. The children are sitting with their legs tucked under, which is caused by the significant muscle tone that they experience.

Children differ and have a characteristic appearance with blond hair, their skin is absolutely white, without pigmentation, their eyes are bright. Considering the excessive whiteness of the skin, it is often covered in rashes in children, which is explained by its special sensitivity to the effect of ultraviolet radiation.

Among the main manifestations of phenylketonuria, one can also distinguish a characteristic «mouse» odor, in some cases, epileptic seizures are possible, which, however, disappear with age. Expressed manifestations are cyanosis of the extremities, dermographism (a change in the color of the skin of a local type that occurs when a mechanical effect on it), sweating. More often among patients with phenylketonuria, in addition to these symptoms, the presence of arterial hypotension, dermatitis, frequent constipation, tremor (ie, trembling), loss of balance and disorder in the form of impaired coordination of movements.

Diagnosis of phenylketonuria

An important, as we have already noted, is the early diagnosis of the disease, which will avoid its development and lead to a number of irreversible and severe consequences. For this reason, blood is taken for blood test in maternity hospitals for 4-5 days of life (for newborns full-term). In preterm infants for phenylketonuria (PKU), blood is taken for 7 days.

The procedure involves taking a capillary blood after an hour after feeding, in particular it impregnates a special form. Concentration pointing to a mark of more than 2.2% phenylalanine in the baby’s blood, requires sending it to the parents for examination in the medical genetic center. In the same place, a further examination and, in fact, a clarification of the diagnosis are carried out.

Causes of phenylketonuria

Phenylketonuria can be triggered by the following factors:


  • Close-knit marriages, in which, in addition to other pathologies, the likelihood of having a child with this disease increases;
  • Mutation of the gene (ie its change), which occurred for one reason or another in the localization of the 12 chromosomes

The very process of inheriting the PKU gene can be random.




Treatment of phenylketonuria

The only method of treatment is the timely organization of diet therapy, which is required from the first days of life. It is in the sharp restriction of phenylalanine, which is contained in individual foods. Thus, all protein products are excluded. Given the duration and complete elimination of phenylalanine from food, it becomes possible to split their own proteins, which leads to the exhaustion of the patient’s body. For this reason, the need for protein production is compensated for by amino acid mixtures and protein hydrolysates.

With a decrease in the concentration in the blood of phenylalanine to normal levels, foods of animal origin are gradually added to the diet. The diet adds a variety of fruits and seasonal vegetables, vegetable and animal fats, as well as carbohydrates. Naturally, the control over the content of phenylalanine should continue to be maintained. The body should be provided with this amino acid in the proper volume for the usual development and growth of the baby, however, with the exception of the possibility of its accumulation in the tissues.

The strictest diet is observed for at least five years. As for the age of the more adult, here the susceptibility of the nervous system to the action exerted by phenylalanine, as well as the effect exerted by its decay products, is greatly reduced. If the required measures are met by the age of 12-14, the child will be able to freely switch to normal nutrition.

It is noteworthy that drug treatment for this disease is syndromic. It includes the use of drugs that focus on the elimination of seizures, including drugs that have a stimulating effect on intellectual activity. In mandatory order, children are prescribed a course of therapeutic physical training and massage. Additionally, lessons are provided that promote the development of logic.




Diagnosis of phenylketonuria is performed by a pediatrician and a geneticist on the basis of special tests in combination with general characteristic symptoms.