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Key Features

  • Characteristics of primary disaccharidase deficiency include

    • Permanent disaccharide intolerance

    • Absence of intestinal injury

    • Frequent positive family history

  • Transient secondary disaccharidase deficiency may be caused by mucosal damage, such as from acute viral enteritis

  • Genetic lactase deficiency develops in

    • Virtually all Asians, Alaskan natives, and Native Americans

    • 80% of Africans

    • 70% of African Americans

    • 30–60% of white Americans

  • Congenital lactase deficiency is extremely rare

  • Sucrase-isomaltase deficiency

    • Inherited in an autosomal recessive fashion

    • Most common in Greenland, Iceland, and among Alaskan natives

    • Condition is rare in other groups

Clinical Findings

  • Lactase deficiency

    • Variable degrees of diarrhea

    • Abdominal distention

    • Flatus

    • Abdominal pain

  • Sucrase-isomaltase deficiency

    • Abdominal distention

    • Failure to thrive

    • Watery, acidic diarrhea


  • Lactase deficiency

    • Stools are liquid or frothy and acidic

    • May test positive for reducing substances

    • Diagnostic tests include genetic testing and lactose breath test

  • Sucrase-isomaltase deficiency

    • Because sucrose is not a reducing sugar, stool may test negative for reducing substances unless the sucrose is hydrolyzed by colon bacteria

    • Diagnosis is made by oral sucrose breath hydrogen testing (1 g/kg), or by testing a snap frozen intestinal biopsy for enzyme activity

    • Partial enzyme deficiencies exist


  • Lactase deficiency

    • Dietary avoidance of lactose or with lactase supplementation

    • Transient or secondary lactase deficiency caused by mucosal injury such as an acute viral gastroenteritis resolves within a few weeks

  • Sucrase-isomaltase deficiency

    • Avoidance of sucrose and starches rich in amylopectin

    • Use of sacrosidase enzyme supplement

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