Each column keeps its native condition scope. Initial features are displayed alphabetically, not ranked by clinical importance. Counts remain separate, and an empty cell does not mean a feature cannot occur.
"},"coverage":{"countRecords":0,"emptyColumnKeys":[],"hpoRelease":"2026-06-23","narrativeSourceChanges":[],"records":5,"sourceGroups":{"omim":0,"orphanet":0,"published":5}},"features":[{"hpoId":"HP:0025130","label":"Decreased small intestinal mucosa lactase level","primary":false},{"hpoId":"HP:0001944","label":"Dehydration","primary":false},{"hpoId":"HP:0002014","label":"Diarrhea","primary":false},{"hpoId":"HP:0004789","label":"Lactose intolerance","primary":false},{"hpoId":"HP:0001942","label":"Metabolic acidosis","primary":false}],"ledeHtml":"Lactose intolerance is a condition that makes it difficult to digest lactose, a sugar found in milk and several other dairy products. Lactose is normally broken down by an enzyme called lactase, which is produced by cells in the lining of the small intestine. Lack or loss of lactase has both genetic and non-genetic causes.","mondoId":"MONDO:0009115","records":[{"frequencyKind":"reported","key":"24ff4939a66a5934c07ee9467f9fef789c4231cd7220e1bab8a3bdd0d42027b7","raw":{"aspect":"P","body_system":"digestive","disease_id":"OMIM:223000","disease_name":"Lactase deficiency, congenital","evidence":"PCS","frequency_raw":null,"hpo_id":"HP:0002014","is_excluded":false,"label":"Diarrhea","onset_id":null,"reference":"PMID:16400612","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"reported","key":"2b8610e62fbf223150db42127f6686e47123e2e2161b59eaf60aefc8bd22b6af","raw":{"aspect":"P","body_system":"digestive","disease_id":"OMIM:223000","disease_name":"Lactase deficiency, congenital","evidence":"PCS","frequency_raw":null,"hpo_id":"HP:0004789","is_excluded":false,"label":"Lactose intolerance","onset_id":null,"reference":"PMID:16400612","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"reported","key":"6c83e51c10a152e06a59d6ef32a0f4646965535faf3b8d44675fa382203724fe","raw":{"aspect":"P","body_system":"metabolic","disease_id":"OMIM:223000","disease_name":"Lactase deficiency, congenital","evidence":"PCS","frequency_raw":null,"hpo_id":"HP:0001942","is_excluded":false,"label":"Metabolic acidosis","onset_id":null,"reference":"PMID:16400612","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"reported","key":"90cca9526f93c9c937350f512e713f654112655f04e9c4043cef16210ff2f8c1","raw":{"aspect":"P","body_system":"metabolic","disease_id":"OMIM:223000","disease_name":"Lactase deficiency, congenital","evidence":"PCS","frequency_raw":null,"hpo_id":"HP:0001944","is_excluded":false,"label":"Dehydration","onset_id":null,"reference":"PMID:16400612","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"reported","key":"9a393a2aa000751086eccab5d0f152e49d0217d3fdba37cb90713dbc2cdbff05","raw":{"aspect":"P","body_system":"metabolic","disease_id":"OMIM:223000","disease_name":"Lactase deficiency, congenital","evidence":"PCS","frequency_raw":null,"hpo_id":"HP:0025130","is_excluded":false,"label":"Decreased small intestinal mucosa lactase level","onset_id":"HP:0003577","reference":"PMID:16400612","source_release":"2026-06-23"},"sourceGroups":["published"]}],"referenceLabels":{},"references":{"causeHtml":"","identityNote":"MONDO cross-references identify native condition entries. Ancestor membership does not transfer phenotype values between groups.","importantHtml":""},"sections":[{"bodyHtml":"Congenital lactase deficiency is caused by variants (also called mutations) in the LCT gene. The LCT gene provides instructions for making the lactase enzyme. Variants in the LCT gene that cause congenital lactase deficiency are believed to interfere with the processing and function of lactase, causing affected infants to have a severely impaired ability to digest the lactose in breast milk or formula.
Lactase nonpersistence in adulthood is caused by the gradually decreasing activity (expression) of the LCT gene after infancy, which occurs in most humans. LCT gene expression is controlled by a DNA sequence called a regulatory element, which is located within a nearby gene called MCM6. Some individuals have inherited changes in this element that lead to sustained lactase production in the small intestine and the ability to digest lactose throughout life. People without these changes have a reduced ability to digest lactose as they get older, resulting in the signs and symptoms of lactase nonpersistence.
","key":"forms","title":"What causes Lactose intolerance?"},{"bodyHtml":"Congenital lactase deficiency, also called congenital alactasia, is a disorder in which infants are unable to break down the lactose in breast milk or formula. This form of lactose intolerance results in very severe diarrhea. If affected infants are not given a lactose-free infant formula, they may experience severe dehydration and weight loss.
Lactose intolerance in adulthood can be caused by the reduced production of lactase after infancy (lactase nonpersistence). If individuals with lactose intolerance consume lactose-containing dairy products, they may experience abdominal pain, bloating, flatulence, nausea, and diarrhea beginning 30 minutes to 2 hours later.
Most people with lactase nonpersistence retain some lactase activity and can include varying amounts of lactose in their diets without experiencing symptoms. Often, affected individuals have difficulty digesting fresh milk but can eat certain dairy products such as cheese or yogurt without discomfort. These foods are made using fermentation processes that break down much of the lactose in milk.
Source: MedlinePlus Genetics
","key":"overview","title":"Condition overview"}],"sharedSources":[],"slug":"lactose-intolerance","sourceDocuments":[{"name":"Lactose intolerance","reviewed":"2023-03","sections":{"causes":{"fetchedAt":"2026-10-20T20:22:46.764902+00:00","label":"Causes","pageSha256":"1c8e417a92794599fa92697b11dd296a84aa981d4aa0a8a179afda818abb7c5b","sourceUrl":"https://medlineplus.gov/genetics/condition/lactose-intolerance/#causes","status":"available"}},"source_release":"2026-10-01","url":"https://medlineplus.gov/genetics/condition/lactose-intolerance"}],"sourceNote":"MedlinePlus descriptions and Causes; original HPO annotations.","takeawayHtml":"Cause explanations are from MedlinePlus Genetics. Feature values below retain their original sources and patient groups.","title":"Lactose intolerance"},"schemaVersion":1}