Phenotypes associated with the disease congenital lactase deficiency (OMIM:223000):
- Diarrhea (HP:0002014): Abnormally increased frequency (usually defined as three or more) loose or watery bowel movements a day. Evidence: PCS. (PMID:16400612)
- 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. Onset: Congenital onset (HP:0003577). (PMID:16400612)
- Dehydration (HP:0001944). Evidence: PCS. (PMID:16400612)
- Autosomal recessive inheritance (HP:0000007): 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 individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele). Evidence: PCS. (PMID:16400612)
- Metabolic acidosis (HP:0001942): Metabolic acidosis (MA) is characterized by a fall in blood pH due to a reduction of serum bicarbonate concentration. This can occur as a result of either the accumulation of acids (high anion gap MA) or the loss of bicarbonate from the gastrointestinal tract or the kidney (hyperchloremic MA). By definition, MA is not due to a respirary cause. Evidence: PCS. (PMID:16400612)
- Lactose intolerance (HP:0004789): An inability to digest lactose. Evidence: PCS. (PMID:16400612)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. (PMID:16400612)