Histidemia

The disease was described in 1961. It is transmitted by an autosomal recessive type of inheritance and is due to a deficiency of the histidase enzyme. This enzyme in the body is contained mainly in its quantity in the liver and the surface layer of the skin, participates in the exchange of the amino acid histidine, transferring it to urocaninic acid. Several variants of the disease are supposed to exist: with an enzyme deficiency in the liver and skin, with a deficiency of the enzyme in the liver and normal activity in the skin. As a result of the disruption of amino acid metabolism, it accumulates in the tissues and body fluids. In addition, the body accumulates a large number of toxic acids that are derivatives of histidine. This disease refers to screening. Mass screening for histidemia was carried out in various countries around the world.

Symptoms of the disease appear in a child usually in the first-second years of life. Typical signs include symptoms of delayed psychomotor and speech development, decreased muscle tone, convulsive syndrome. In older children, intellectual disorders and speech disorders are at the forefront. The majority of sick children have characteristic external features: blonde hair, blue eyes.

Due to the fact that as a result of mass screening in different regions of the world, a certain number of children with hyperhistidinemia without any symptoms were identified, the question arose: is not this disease an inoffensive biochemical disorder? However, recent studies have confirmed the relationship between metabolic disturbances and damage to the nervous system.

The diagnosis of histidemia is established on the basis of the determination of an elevated level of this amino acid in blood and urine, the appearance of an inadequate reaction of the body to the load with histidine, which consists in an increase in its content in blood serum and in urine. Special methods establish a decrease in the activity of the enzyme histidase in the skin. In addition, there are ways to determine this enzyme in the liver. The last two methods of investigation are specific and are conducted only in highly specialized hospitals for the study of hereditary pathology.

For prenatal diagnosis of the disease, it is possible to determine the activity of histidase in amniotic fluid cells.

Treatment of disease, as well as in the case of phenylketonuria, consists mainly of observing a diet with restriction of the amino acid histidine. In this case, the probability of developing a child's convulsive syndrome is reduced, while the probability of intellectual and speech disorders remains at the same level.