Lactose intolerance is characterized by reduced lactase concentration in the mucosal brush border of the small intestine (also known as hypolactasia).
It exists in four distinct forms: primary, secondary, congenital, and developmental.
Symptoms can be gastrointestinal and/or systemic.
Dietary elimination and challenge are generally diagnostic.
Treatment includes reduction or elimination of dietary lactose.
If elimination of lactose is necessary, alternative calcium sources are recommended.
Lactose intolerance refers to the development of gastrointestinal and/or systemic symptoms secondary to malabsorption of lactose caused by hypolactasia. It is characterized by reduced lactase (lactase-phlorizin hydrolase enzyme) concentration in the mucosal brush border (microvilli) of the small intestine, usually at the age of weaning. Malabsorption of lactose, however, does not always manifest as gastrointestinal symptoms; development of symptoms and symptom severity depend on the amount and rate of lactose reaching the colon, as well as the type and amount of colonic flora.
History and exam
- black, Native American, Asian, or Hispanic ethnicity
- adolescence and early adulthood
- family history of lactase deficiency
- comorbid predisposing disease
- history of irritable bowel syndrome diagnosis
- symptoms after ingestion of dairy products
- mouth ulceration
- poor short-term memory
- poor concentration
- muscle/joint pain
- failure to thrive
- abdominal pain/discomfort
- skin rashes
- history of asthma
- history of peptic ulcer disease
- history of gastroesophageal reflux disorder
- weight loss
- short stature
- progressive disability
- sensory loss
- hair loss
Dr Anton Emmanuel, MD, FRCP
University College London
University College Hospital and the National Hospital for Neurology and Neurosurgery (Queen Square)
AE declares that he has no competing interests.
Dr Anton Emmanuel would like to gratefully acknowledge Dr Mohammad Azam and Dr Richard J. Farrell, previous contributors to this monograph. MA and RJF declare that they have no competing interests.
Anthony Lembo, MD
Assistant Professor of Medicine
Harvard Medical School
Beth Israel Deaconess Medical Center
AL declares that he has no competing interests.
Michele Di Stefano, MD
Coordinator of the Gastrointestinal Motility Laboratory
University of Pavia
1st Division of Medicine
IRCCS S. Matteo Hospital Foundation
MDS is the author of references cited in this topic.
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