Giperammoniyemiya
Contents:
Description:
Giperammoniyemiya is the hereditary disease of a metabolism which is shown in insufficiency of a cycle of enzymes of urea, leading to organism poisoning with ammonia.
Ammonia is the toxic connection which is in blood in rather small concentration (11,0-32,0 µmol/l). Symptoms of ammoniac poisoning are shown at exceeding of these limits by only 2-3 times. Maximum permissible level of ammonia in blood of 60 µmol/l. At increase in concentration of ammonia (giperammoniyemiya) up to the extreme sizes there can come the coma and death. At a chronic giperammoniyemiya mental retardation develops.
Giperammoniyemiya's symptoms:
Tranzitorny giperammoniyemiya is called also borderline case inherent in newborn children during adaptation to an extrauterine life which is shown usually on the second – thirds days of life. This type of a giperammoniyemiya occurs most often at premature children with a delay of pre-natal development, with a frequency up to fifty percent of births, however sometimes is registered also at the full-term kids. A part of children does not show symptomatology of a clinical picture of a giperammoniyemiya: signs of oppression of the central nervous system (slackness, decrease in a muscle tone, apnoea attacks, the weakened reaction of pupils to light, refusal of food, a stupor and a coma), and also disorders of respiratory function, jaundice, spasms and dehydration. The reason causing a giperammoniyemiya call air hunger, or a hypoxia, during pregnancy and in the course of childbirth.
The acquired forms
The giperammoniyemiya acquired (secondary) develops owing to diseases of a liver and viral infections. In extremely hard cases it is shown as nausea, vomiting, spasms, the inarticulate speech, sight misting, a tremor, a lack of coordination of movements.
Hereditary forms
Hereditary forms of a giperammoniyemiya are caused by genetic defect of any of five enzymes of synthesis of urea. According to enzyme the disease is divided into five types. Primary signs of giperammoniyemiya are drowsiness, refusal of food, vomiting, concern, spasms, an incoordination of movements, a tachypnea, a respiratory alkalosis. The liver failure, pulmonary and intracraneal hemorrhages can develop.
The most frequent is the giperammoniyemiya of type II connected with a shortcoming ornithine-karbamoiltransferazy. The disease retsessivno, is linked to X-chromosome. At mother the giperammoniyemiya and disgust for proteinaceous products is also observed. At a total defect of enzyme hereditary giperammoniyemiya have the early beginning (during the period till 48 o'clock after the birth).
Laboratory criterion of a disease is accumulation of a glutamine (in 20 and more times) and ammonia in blood, liquor and urine.
The basis of treatment of giperammoniyemiya comes down to restriction of protein in a diet, already it allows to prevent many disturbances of brain activity.
Giperammoniyemiya's reasons:
Toxicity of ammonia is caused by the following circumstances:
1. Binding of ammonia at synthesis of a glutamate causes outflow of α-ketoglutarate from a cycle of tricarboxylic acids, at the same time formation of energy of ATP goes down and activity of cells worsens.
2. Ions of NH4+ ammonium cause alkalinization of a blood plasma. At the same time affinity of hemoglobin to oxygen increases (Bohr effect), hemoglobin does not give oxygen in capillaries, the hypoxia of cells is caused.
3. Accumulation of a free ion of NH4+ in cytosol influences the membrane potential and work of desmoenzymes – it competes with ionic pumps for Na + and K+.
4. The product of linkng of ammonia with glutaminic acid – a glutamine – is osmotically active agent. It leads to a water delay in cells and to their swelling that causes hypostasis of fabrics. In case of nervous tissue it can cause wet brain, a coma and death.
5. Use of α-ketoglutarate and a glutamate for neutralization of ammonia causes decrease in synthesis of γ-aminobutyric acid of acid (GAMK), a brake mediator of a nervous system.
Giperammoniyemiya's treatment:
As a rule, the similar state does not demand any specific treatment, however in separate hard cases the newborn with a pathological giperammoniyemiya zamenny hemotransfusion, the procedure of dialysis becomes and symptomatic therapy is appointed.
