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Sugar-isomaltase deficiency

Alexey Kryvenko, medical expert
Last reviewed: 04.07.2025

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Three phenotypes of congenital enzyme deficiency caused by mutations in the gene controlling the synthesis of the enzyme complex have been described. Data on the localization of this gene in chromosome 3 have been published. Pathogenetic changes are similar to lactase deficiency, with the difference that sucrose and isomaltose are not prebiotics, and disruption of their breakdown leads more quickly to the development of intestinal dysbiosis. The disease manifests itself in the first month of life only with artificial feeding with products containing starch, dextrins (maltodextrin), sucrose, or when the child is given water with added sugar. Usually, the disease manifests itself after the introduction of complementary foods.

ICD-10 code

E74.3. Other disorders of intestinal carbohydrate absorption.

Diagnostics

The diagnostics is based on the increase of starch content in coprological examination, the increase of carbohydrate concentration in stool. The "gold standard" of diagnostics, as in lactase deficiency, is considered to be the determination of enzyme activity in a biopsy of the small intestinal mucosa. This method allows differentiating between different types of disaccharidase deficiency.

Treatment

Treatment consists of an elimination diet with the exclusion of sucrose, dextrin, starch, and table sugar.

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