Lactase deficiency can be primary, secondary, or congenital.
- Primary – Low levels of lactase enzyme. Symptom onset may be in childhood or adulthood.
- Secondary – Reversible lactase deficiency caused by mucosal injury, often in the setting of viral illnesses.
- Congenital – A rare autosomal recessive absence of lactase activity at birth leading to diarrhea and hypercalcemia in infancy, predisposing patients to nephrocalcinosis.
E73.9 – Lactose intolerance, unspecified
782415009 – Intolerance to lactose
- Infectious gastroenteritis (bacterial, viral, helminth)
- Congenital lactase deficiency
- Celiac disease
- Small intestinal bacterial overgrowth
- Inflammatory bowel disease (ulcerative colitis, Crohn disease)
- Irritable bowel syndrome
- Anxiety disorders
- Biliary colic
- Chronic mesenteric ischemia
- Chronic pancreatitis
- Collagenous gastritis
- Collagenous colitis
- Lymphocytic colitis
- Colon cancer
- Food allergies
- Malignancy: gastric, small bowel, or large bowel
- Pancreatic cancer
- Postcholecystectomy syndrome
- Bile acid diarrhea
- Laxative abuse
- Cow milk allergy