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Related to alactasia: Hypolactasia
congenital lactase deficiencyA rare, autosomal recessive gastrointestinal disorder (OMIM:223000) characterised by severe watery diarrhoea in infants fed with breast milk or other lactose-containing formulas. A virtually complete lack of LCT activity is found in jejunal biopsy material.
In contrast, adult-type hypolactasia (lactose intolerance), the most common enzyme deficiency worldwide, is due to a developmental downregulation of lactase activity that evolves from childhood to early adulthood, and which is regarded as a normal physiological phenomenon. Most northern Europeans maintain lactase activity and digest lactose throughout life, a phenomenon known as lactase persistence.
Defects of LCT, which encodes lactase, a glycosyl hydrolase, cause congenital lactase deficiency.