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Genetic and Rare Diseases Information Center (GARD)

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Congenital sucrase-isomaltase deficiency

Other Names for this Disease
  • Congenital sucrose-isomaltase malabsorption
  • CSID
  • Disaccharide intolerance, 1
  • SI deficiency
  • Sucrase-isomaltase deficiency, congenital
More Names
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Tests & Diagnosis

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How is congenital sucrase-isomaltase deficiency (CSID) diagnosed?

CSID can be diagnosed through clinical evaluation, detailed patient history, and tolerance lab tests. Blood tests can be done to look for a flat serum glucose curve after patients are given a dose of sucrose. In addition, blood and urine samples may test positive for sucrose, maltose, or palatinose (a form of maltose) if used during tolerance testing. The feces may also show sucrose, glucose, and fructose, and an acid pH level of below 5.0 or 6.0.[1] 

CSID can be confirmed by taking a small sample of tissue (biopsy) from the small intestine and measuring the activity of the enzyme called sucrase-isomaltase. Other tests may include a sucrose hydrogen breath test in which an abnormally high level of hydrogen will be detected in the breath of an affected individual after sucrose ingestion.[1]
Last updated: 7/5/2013

  1. Disaccharide Intolerance I. National Organization for Rare Disorders. April 25, 2008; Accessed 7/5/2013.