Inherited or acquired disorders of sugar metabolism. Deficiencies of lactase, maltase or sucrase-isomaltase usually occur irreversibly and independent of one another. Congenital deficiencies are rare whereas acquired deficiencies are more common and may be seen following intestinal mucosal brush-border injury. Clinical signs include abdominal cramping, bloating, flatulence and diarrhea following dietary intake of lactose, maltose or sucrose. The clinical course leads to malabsorption of disaccharides which has implications for normal growth and development if manifested at an early age. The disease is intestinal disaccharidase deficiency (MONDO_0004905). Also known as: intestinal disaccharidase deficiency and disaccharide malabsorption.