LCT and hyperinsulinemic hypoglycemia, familial, 4: The defects of intestinal digestion of di- and oligo-saccharides (like congenital sucrase-isomaltase or lactase deficiency) or defects in the absorption of monosaccharides (like congenital glucose-galactose deficiency) lead to fermentative diarrhea, which constitutes the major symptoms associated with malabsorption.