Lactose intolerance.

Lactose intolerance is due to low levels of lactase-phlorizin hydro- lase (LPH) in the brush border of the small-intestinal enterocytes with the consequent inability to digest lactose into its constituents, glucose and galactose. Two forms with deficiency of lactase are recognized: the adult lactase deficiency and the congenital lactase deficiency (CLD). A third condition of lactose intolerance having serious conse- quences in infants but associated with a normal presence of lactase in enterocytes is the congenital lactose intolerance.