Lactase deficiency in children

Lactose intolerance is a disease that causes malabsorption syndrome (watery diarrhea) and is caused by a disruption in the breakdown of lactose in the small intestine.

Primary lactase deficiency is a decrease in lactase activity with an intact enterocyte. Primary lactase deficiency includes congenital lactase deficiency, adult-type lactase deficiency, and transient lactase deficiency in premature infants.

Secondary lactase deficiency is a decrease in lactase activity associated with enterocyte damage. Enterocyte damage is possible with an infectious or allergic (for example, sensitization to cow's milk proteins) inflammatory process in the intestine, as well as with a decrease in the enterocyte pool due to a decrease in the area of the intestinal mucosa due to villous atrophy, a decrease in the length of the jejunum after resection, or with congenital short bowel syndrome.

Congenital alactasia is a rare disorder caused by a mutation outside the LCT gene, which codes for lactase synthesis. Cases of this disorder, called "Finnish-type recessive disorders", have been described in Finland. Transient lactase deficiency of prematurity is associated with low enzyme activity in children born before 34-36 weeks of gestation.

Secondary lactase deficiency often occurs in young children against the background of infectious and allergic diseases as a component of post-resection syndrome in a number of intestinal developmental anomalies. Brush border lactase, compared to other disaccharidases, is located closer to the top of the villi, especially in the duodenum, which determines the frequency of lactase deficiency compared to the deficiency of other enzymes in case of damage to the mucous membrane of any etiology.

ICD-10 codes

• E73.0. Congenital lactase deficiency.
• E73.1. Secondary lactase deficiency.
• E73.8. Other types of lactose intolerance.

Symptoms of lactose intolerance

Undigested lactose entering the large intestine causes flatulence and bloating due to the formation of a large amount of gases during fermentation. In small children, flatulence can cause regurgitation, but this is uncharacteristic of isolated lactase deficiency. When the amount of lactose consumed exceeds the utilization capacity of bacteria, osmotic diarrhea develops. Characteristic is digested stool of a yellow color with a sour smell, liquefied, foamy. Pathological impurities are absent. In primary lactase deficiency, the severity of clinical symptoms clearly correlates with the dose of lactose consumed. The severity of the clinical picture increases with an increase in the amount of milk consumed. Anxiety is characteristic a few minutes after the start of feeding while maintaining a good appetite. A different situation occurs when the amount of lactic acid microflora decreases. In this case, the compensatory capabilities of the lactose-utilizing microflora are reduced, diarrhea occurs with smaller amounts of undigested lactose, the pH in the intestine shifts to the alkaline side, which aggravates dysbacteriosis. This situation is typical for a combination of primary lactase deficiency with intestinal dysbacteriosis or secondary lactase deficiency and intestinal infection. In these cases, the stool may contain pathological impurities (mucus, greenery). With diarrhea, exicosis and hypotrophy may develop, especially with congenital alactasia. The occurrence of acidosis, persistent vomiting, aminoaciduria is not typical for isolated primary lactase deficiency; such symptoms require differential diagnosis with hereditary metabolic disorders and other diseases.

Diagnosis of lactase deficiency

The basis for the diagnosis of lactase deficiency is the assessment of the clinical picture, diet during the manifestation of the disease (whether the child received lactose with food), the search for factors leading to secondary lactase deficiency. Deviations from the norm of the results of the studies listed below without clinical symptoms do not require treatment.

• Determination of the carbohydrate content in feces reflects the general ability to assimilate carbohydrates. The method does not allow differentiating between different types of disaccharidase deficiency, but together with clinical data it is sufficient for screening and monitoring the correctness of diet selection. In infancy, the carbohydrate content in feces should not exceed 0.25%. In children over 1 year old, this test should be negative.
• _{Determination of the content of} hydrogen, methane or labeled ^11C CO2 in exhaled air. The methods reflect the activity of microflora in lactose fermentation. It is advisable to determine the concentration of gases after a dosed load of regular or labeled lactose. The diagnostic criterion for adults and older children is an increase in hydrogen in exhaled air after a lactose load of 20 ppm (parts per million).
• Lactose loading tests determine glycemia recorded before and after lactose loading at a dose of 2 g/kg of body weight. In lactase deficiency, there is a flat or flattened type of glycemic curve (normally, the increase in glycemia is more than 1.1 mmol/l). Lactose loading tests are of little use for diagnosing lactase deficiency in situations where absorption disorders and damage to the intestinal mucosa can be assumed.

• The method for determining lactase activity in biopsies or swabs from the small intestinal mucosa is free from the shortcomings of previous methods. This method is considered the "gold standard" for diagnosing lactase deficiency, but the invasiveness of the method limits its use.
• Molecular genetic diagnostics based on the detection of intron gene mutations has been developed for "adult-type" lactase deficiency. The test is considered economically feasible and is performed once, which is more convenient for the patient than load tests. In children under 12, the method can only be used to exclude lactase deficiency. Differential diagnostics are performed with watery diarrhea of other etiologies.

Treatment of lactase deficiency

The treatment of lactase deficiency is based on diet therapy - limiting lactose consumption, the degree of reduction is selected taking into account the excretion of carbohydrates with feces. In diseases that lead to secondary lactase deficiency, the main attention should be paid to the treatment of the underlying disease. Reducing the amount of lactose in the diet serves as a temporary measure necessary to restore the mucous membrane of the small intestine.

In young children, the most rational tactic is considered to be an individual step-by-step selection of the amount of lactose in the diet. Lactose should not be completely excluded from the child's diet, even if congenital lactase deficiency is detected, since lactose serves as a prebiotic and a source of galactose. If the child is breastfed, the optimal way to reduce lactose consumption is considered to be the use of lactase preparations mixed with expressed breast milk. For children under 1 year, the use of the food supplement "Lactase Baby" is allowed. The drug is given at each feeding (770-800 mg of lactase or 1 capsule of "Lactase Baby" for every 100 ml of milk), starting with a portion of expressed milk with lactase, and then the child is fed from the breast.

For children on artificial or mixed feeding, it is necessary to select food with the maximum amount of lactose that does not cause digestive disorders and an increase in the carbohydrate content in the stool. Individual selection of a diet is carried out by combining a lactose-free product and a standard adapted formula in a ratio of 2:1, 1:1 or 1:2. In the absence of an allergy to cow's milk proteins, lactose-free adapted milk formulas are used, in the presence of an allergy - formulas based on deep protein hydrolysate. In case of severe lactase deficiency, ineffectiveness of reducing the amount of lactose by half, low-lactose or lactose-free products are used as monotherapy. In case of secondary lactase deficiency against the background of food allergy, dietary correction should begin with lactose-free formulas based on complete protein hydrolysate. Formulas based on soy protein are not considered the drugs of choice in the dietary therapy of lactase deficiency.

Prevention of celiac disease in children consists of late (after 8 months of life) introduction of semolina and oatmeal into the diet, prevention of exacerbations - long-term adherence to the agliadin diet.

Outpatient observation is carried out for life. Diet and replacement therapy are adjusted, growth and body weight dynamics are monitored, coprogram is assessed, massage and exercise therapy are performed.

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