Sudden lactose intol. Defects in lactose absorption can be acquired (due to inflammatory conditions of the intestine*) or congenital. Adult lactase deficiency (hypolactasia) is autosomal recessive (ar) & present in >75% of non-caucasians & 20% of caucasians. Congenital lactase deficiency (ar) is acute watery diarrhea in infants. *see your doctor for evaluation if your lactose intolerance is indeed of sudden onset.