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Yin, N. Congenital Sucrase-Isomaltase Deficiency. Encyclopedia. Available online: (accessed on 20 June 2024).
Yin N. Congenital Sucrase-Isomaltase Deficiency. Encyclopedia. Available at: Accessed June 20, 2024.
Yin, Nicole. "Congenital Sucrase-Isomaltase Deficiency" Encyclopedia, (accessed June 20, 2024).
Yin, N. (2020, December 24). Congenital Sucrase-Isomaltase Deficiency. In Encyclopedia.
Yin, Nicole. "Congenital Sucrase-Isomaltase Deficiency." Encyclopedia. Web. 24 December, 2020.
Congenital Sucrase-Isomaltase Deficiency

Congenital sucrase-isomaltase deficiency is a disorder that affects a person's ability to digest certain sugars. People with this condition cannot break down the sugars sucrose and maltose.

genetic conditions

1. Introduction

Sucrose (a sugar found in fruits, and also known as table sugar) and maltose (the sugar found in grains) are called disaccharides because they are made of two simple sugars. Disaccharides are broken down into simple sugars during digestion. Sucrose is broken down into glucose and another simple sugar called fructose, and maltose is broken down into two glucose molecules. People with congenital sucrase-isomaltase deficiency cannot break down the sugars sucrose and maltose, and other compounds made from these sugar molecules (carbohydrates).

Congenital sucrase-isomaltase deficiency usually becomes apparent after an infant is weaned and starts to consume fruits, juices, and grains. After ingestion of sucrose or maltose, an affected child will typically experience stomach cramps, bloating, excess gas production, and diarrhea. These digestive problems can lead to failure to gain weight and grow at the expected rate (failure to thrive) and malnutrition. Most affected children are better able to tolerate sucrose and maltose as they get older.

2. Frequency

The prevalence of congenital sucrase-isomaltase deficiency is estimated to be 1 in 5,000 people of European descent. This condition is much more prevalent in the native populations of Greenland, Alaska, and Canada, where as many as 1 in 20 people may be affected.

3. Causes

Mutations in the SI gene cause congenital sucrase-isomaltase deficiency. The SI gene provides instructions for producing the enzyme sucrase-isomaltase. This enzyme is found in the small intestine and is responsible for breaking down sucrose and maltose into their simple sugar components. These simple sugars are then absorbed by the small intestine. Mutations that cause this condition alter the structure, disrupt the production, or impair the function of sucrase-isomaltase. These changes prevent the enzyme from breaking down sucrose and maltose, causing the intestinal discomfort seen in individuals with congenital sucrase-isomaltase deficiency.

4. Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

5. Other Names for This Condition

  • congenital sucrose intolerance
  • congenital sucrose-isomaltose malabsorption
  • CSID
  • disaccharide intolerance I
  • SI deficiency
  • sucrase-isomaltase deficiency


  1. Belmont JW, Reid B, Taylor W, Baker SS, Moore WH, Morriss MC, Podrebarac SM,Glass N, Schwartz ID. Congenital sucrase-isomaltase deficiency presenting withfailure to thrive, hypercalcemia, and nephrocalcinosis. BMC Pediatr. 2002 Apr25;2:4.
  2. Jacob R, Zimmer KP, Schmitz J, Naim HY. Congenital sucrase-isomaltasedeficiency arising from cleavage and secretion of a mutant form of the enzyme. J Clin Invest. 2000 Jul;106(2):281-7.
  3. Keiser M, Alfalah M, Pröpsting MJ, Castelletti D, Naim HY. Altered folding,turnover, and polarized sorting act in concert to define a novel pathomechanismof congenital sucrase-isomaltase deficiency. J Biol Chem. 2006 May19;281(20):14393-9.
  4. Ritz V, Alfalah M, Zimmer KP, Schmitz J, Jacob R, Naim HY. Congenitalsucrase-isomaltase deficiency because of an accumulation of the mutant enzyme in the endoplasmic reticulum. Gastroenterology. 2003 Dec;125(6):1678-85.
  5. Sander P, Alfalah M, Keiser M, Korponay-Szabo I, Kovács JB, Leeb T, Naim HY.Novel mutations in the human sucrase-isomaltase gene (SI) that cause congenitalcarbohydrate malabsorption. Hum Mutat. 2006 Jan;27(1):119.
  6. Sibley E. Carbohydrate intolerance. Curr Opin Gastroenterol. 2004Mar;20(2):162-7.
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