Insufficiency of vitamin A — the morbid condition arising owing to deficit in an organism of this vitamin and which is shown deterioration in sight — first of all a hemeralopia (a "chicken" blindness), conjunctivitis, a xerophthalmia, a skin hyperkeratosis. The bent to respiratory diseases and intestines is characteristic.
Epidemiology The exogenous form of deficit of vitamin A meets seldom. Endocrine manifestations of a hypovitaminosis And are observed more often, mainly at patients with chronic diseases of intestines, liver, closed glands (a toxic craw, a diabetes mellitus), at the disseminated tuberculosis, a carcinoid syndrome.
Pathogeny Vitamin A comes to an organism with food (see the table) as in pure form, and in the form of provitamins — carotinoids.
Retinolum accelerates oxidizing processes, stimulates activity of gonads, promotes growth of young animals, is an antagonist of thyroxine. This vitamin is necessary for normal functioning of covers of an eye, skin, a mucous membrane of a digestive tract, a bronchial tree and uric ways. He participates in resynthesis of a pigment of rhodopsin (rhodopsin) which is contained in sticks of a mesh cover. At a lack of Retinolum this process is broken owing to what first of all twilight sight suffers — the hemeralopia develops.
Classification There is no standard classification.
Approximate formulation of the diagnosis: 1. Hypovitaminosis And (primary): hemeralopia. 2. Portal cirrhosis in an aggravation phase. A hypovitaminosis And (endogenous), a hemeralopia, the beginning xerophthalmia. 3. Avitaminosis And (food): xerophthalmia, keratomalacia of the left eye, hemeralopia; stomatitis, Limited dermatitis in the field of a dorsum of hands and elbow joints.
Preliminary diagnosis Dryness in an oral cavity and a nose, the xeroderma, its peeling, the raised hair loss are observed. Twilight sight (a "chicken" blindness) worsens. Are at the same time possible a photophobia (eye pain at bright lighting) and a xerophthalmia (dryness of a conjunctiva with loss of gloss inherent in it, decrease in secretion of the lacrimal glands, emergence of plaques of Iskersky — Bito, scattered on a sclera). In the most hard cases inflammatory processes in a cornea can be complicated by its necrotic softening (keratomalacia) that usually comes to an end with a blindness.
The hemeralopia combination to a xerophthalmia allows to think with high reliability of insufficiency of vitamin A.
Verification of the diagnosis Use eye biomicroscopy, determine the content in blood serum of vitamin A or carotene. Investigate dark adaptation of sight which at insufficiency of Retinolum significantly decreases.
The combination of a hemeralopia and xerophthalmia against sharp decrease in content of vitamin A in blood (lower than 100 mkg/l) is characteristic of avitaminosis And. The most dangerous complication of avitaminosis are a keratomalacia with the subsequent blindness, a panophthalmia, and also secondary purulent encephalitis.
At a hypovitaminosis And the content in blood of Retinolum or carotene (lower than 200 mkg/l) is lowered, dark adaptation is broken, the hemeralopia develops. At eye biomicroscopy on mucous conjunctivas can come to light whitish and yellowish small plaques.
Treatment and prevention Appoint the diet rich with vitamin A and provitamins, and also Retinolum drugs. Solutions of Retinolum apply in and in the form of intramuscular injections.
Daily medical dose 25 000 — 100 000 ME Retinolums (at intake the dose is divided into 2 — 3 receptions, more than one injection a day usually do not do), duration of a course of treatment of 2 — 4 weeks. Retinolum contains in polyvitaminic drugs.
At prolonged use of Retinolum in high doses (100 000 ME above in days) intoxication symptoms can develop ("a hypervitaminosis And"): nausea, vomiting, a headache, a dermahemia, hemorrhages in hypodermic cellulose, etc.
Prevention of a hypovitaminosis And consists in a balanced diet and appointment in Retinolum drugs (5000 — 10 000 ME) during not less than 2 — 3 weeks. Before and after the conducted preventive course it is reasonable to determine the content in blood serum of Retinolum or carotene.