Having found out what kind of disease - phenylketonuria, diagnosed during the newborn period, it is required to immediately start treatment when it is detected. Early detection and therapy make it possible to achieve favorable results.
Phenylketonuria - what is this disease?
Phenylketonuria, or Felling's disease, is a serious pathology, first described in 1934 by the Norwegian scientist Felling. Then Felling conducted a survey of several children with mental retardation and revealed in them the presence in the urine of phenylpyruvate, the product of the breakdown of the amino acid phenylalanine, which comes with food, which does not split in the patients' body. Phenylketonuria is a disease associated with a metabolic disorder of an innate nature, discovered one of the first.
Phenylketonuria is a type of inheritance
Felling's disease is a chromosomal-genetic, hereditary, transmitted to children from their parents. The culprit for the development of pathology is the gene located on the 12 chromosome. He is responsible for the production of the hepatic enzyme phenylalanine-4-hydroxylase, through which the conversion of phenylalanine to another substance - tyrosine (it is required for normal body functioning).
It was established that phenylketonuria is inherited as a recessive trait. Approximately 2% of people are carriers of a defective gene, but they do not suffer from phenylketonuria. Pathology develops only when both the mother and father transmit the gene to the child, and this can happen with a probability of 25%. If phenylketonuria is inherited as a recessive trait, the wife is heterozygous, and the husband is homozygous for the normal allele of the gene, then the probability that children will be healthy carriers of the phenylketonuria gene is 50%.
Forms of phenylketonuria
Considering who can develop phenylketonuria, what kind of disease, often it is a classic form of pathology, which occurs in about 98% of cases. The remaining cases - cofactor phenylketonuria, caused by tetrahydrobiopterin defect due to a violation of its synthesis or restoration of the active form. This substance serves as a cofactor of a number of enzymes, and without it, the manifestation of their activity is impossible.
Phenylketonuria - Causes
Felling disease is a pathology in which, due to mutations in the gene that cause deficiency or lack of phenylalanine-4-hydroxylase, there is an accumulation in the tissues and physiological fluids of phenylalanine, as well as the products of its incomplete cleavage. Part of the excess phenylalanine is converted to phenylketones, which are excreted in the urine, which is what determined the name of the disease.
The disturbance of metabolic processes affects mainly the brain. On its tissues, a toxic effect is produced, the processes of fat metabolism are disrupted, the myelination of nerve fibers fails, and the formation of neurotransmitters decreases. So begins the launch of pathogenetic mechanisms of mental retardation in the child.
Phenylketonuria - symptoms
At birth, a child with this diagnosis looks healthy, and only after 2-6 months the first symptoms are found. Phenylketonuria signs begin to manifest when the child's body accumulates phenylalanine, which comes with breast milk or mixtures for artificial feeding. There may be such not yet specific symptoms:
- excessive lethargy or anxiety;
- causeless cries;
- muscular dystonia ;
- frequent regurgitation;
- convulsions ;
- sleep disorders.
In addition, sick babies have a lighter skin, hair and eyes than healthy members of the family, which is associated with a violation of the production of pigment melanin in the body. Another diagnostic sign that physicians or attentive parents can notice is a kind of "mouse" smell caused by the release of phenylalanine in the urine and sweat.
Clinical manifestations become more pronounced at about six months of age, after the introduction of the first complementary meal:
- inability to focus on individual subjects;
- indifference to everything that happens;
- absence of facial expressions, smiles;
- tremor of hands and so on.
Noticeable are also physical abnormalities: a small head size, an outstanding upper jaw, a lag in growth. Sick children later start to hold their heads, crawl, sit down, get up. A special position in the sitting position is typical - the "tailor" posture, with the arms constantly bent at the elbows, and the legs at the knees. At the age of three, if the treatment has not been started, the symptomatology is growing.
Phenylketonuria - Diagnosis
Phenylketonuria in children is often detected in the maternity hospital, which allows to start treatment on time and prevent the development of a number of irreversible consequences. At 4-5 days after birth, babies take capillary blood on an empty stomach to determine some severe genetic diseases, among them - phenylketonuria. If an extract from the maternity hospital occurred earlier, the analysis is done in the polyclinic at the place of residence during the first 10 days of life.
Given that in rare cases, there are erroneous results, the diagnosis is never established following the results of the first analysis. To confirm the existing pathology, a number of other studies are assigned, among which:
- urinalysis for the detection of phenylpyruvate;
- quantitative determination of phenylalanine and tyrosine in plasma;
- determination of hepatic enzyme activity;
- electroencephalography and magnetic resonance imaging of the brain.
A genetic defect leading to the development of pathology can be detected in the fetus during invasive prenatal diagnosis. To do this, samples of cells from villus chorion or amniotic fluid are selected, and then DNA analysis is performed. It is recommended that such a study in families with a high risk of morbidity, including, if already there is a child with phenylketonuria.
Phenylketonuria - treatment
When phenylketonuria is detected in newborns, doctors of such specialties as geneticist, pediatrician, neurologist, nutritionist should observe the sick. Those who know, phenylketonuria - what kind of disease, it will be clear why the basis of his treatment is to follow a diet with a restriction of phenylalanine. In addition, medication, massage, physiotherapy, psychological and pedagogical methods for the socialization of the child, preparation for learning, are prescribed.
Phenylketonuria - diet
When diagnosing "phenylketonuria", a diet for a child is prescribed immediately. From the diet, foods rich in protein (meat, fish, dairy products, legumes, nuts and others) are excluded. The need for proteins is compensated for by special dietary mixtures and other products with berlofen - semisynthetic protein hydrolyzate, completely devoid of phenylalanine (Tetrafen, Lofenalak, Nofelan). Patients take protein-free bread, pasta, cereals, mousses and so on. Breastfeeding is done in limited doses.
Strict adherence to a diet with regular monitoring of the content of phenylalanine in the blood during the first 14-15 years of life prevents the development of mental abnormalities. Then the diet is somewhat expanded, but many experts recommend lifelong observance of a special diet. The cofactor form of phenylketonuria is not treated by diet, but is corrected only by administration of tetrahydrobiopterin preparations.
Phenylketonuria - drugs for treatment
Phenylketonuria treatment in children also provides for the intake of certain drugs, including:
- nootropics ( Piracetam , Cerebrolysin);
- vitamins of group B;
- mineral complexes;
- drugs for improving tissue metabolism (ATP, Riboxin );
- drugs that improve microcirculation (Trental, Pentoxifylline).
Phenylketonuria - prognosis for life and disease
Parents who know firsthand what kind of genetic disease - phenylketonuria, in modern conditions is given the opportunity to grow a healthy child, if you follow all the medical prescriptions. When proper treatment is not available, phenylketonuria prognosis is disappointing: patients live about 30 years with severe mental deficiency and multiple functional disorders.