- Diarrhea (HP:0002014): Abnormally increased frequency (usually defined as three or more) loose or watery bowel movements a day. Evidence: PCS. (PMID:12915462)
- Juvenile onset (HP:0003621): Onset of signs or symptoms of disease between the age of 5 and 15 years. Evidence: PCS. (PMID:12915462)
- Decreased small intestinal mucosa lactase level (HP:0025130): Lactase is produced in the small intestine in humans, Lactase is a member of the beta-galactosidase family of enzymes, and hydrolyzes D-lactose to form D-galactose and D-glucose, which can be absorbed by the small intestine. There are many ways of assessing lactase activity. In one test, an endoscopic biopsy from the postbulbar duodenum is incubated with lactose on a test plate, and a color reaction develops within 20 min as a result of hydrolyzed lactose (a positive result) in patients with normolactasia, whereas no reaction (a negative result) develops in patients with severe hypolactasia. Other, less direct, tests include the hydrogen breath test, and blood tests following lactose challenges. Evidence: PCS. (PMID:11788828)
- Childhood onset (HP:0011463): Onset of disease at the age of between 1 and 5 years. Evidence: PCS. (PMID:12915462)
- Young adult onset (HP:0011462): Onset of disease at the age of between 16 and 40 years. Evidence: PCS. (PMID:12915462)
- Flatulence (HP:0033589): Passage of excessive amounts of gas and the feeling of abdominal fullness and bloating. Evidence: PCS. (PMID:12915462)
- Lactose intolerance (HP:0004789): An inability to digest lactose. Evidence: PCS. (PMID:12915462)
- Abdominal pain (HP:0002027): An unpleasant sensation characterized by physical discomfort (such as pricking, throbbing, or aching) and perceived to originate in the abdomen. Evidence: PCS. (PMID:12915462)
- Autosomal dominant inheritance (HP:0000006): A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele. Evidence: PCS. (PMID:11788828)
These phenotypes are associated with the disease lactose intolerance adult type (OMIM:223100).