Malabsorption Syndromes: General term for a group of MALNUTRITION syndromes caused by failure of normal INTESTINAL ABSORPTION of nutrients.Sprue, Tropical: A chronic malabsorption syndrome, occurring mainly in residents of or visitors to the tropics or subtropics. The failed INTESTINAL ABSORPTION of nutrients from the SMALL INTESTINE results in MALNUTRITION and ANEMIA that is due to FOLIC ACID deficiency.Celiac Disease: A malabsorption syndrome that is precipitated by the ingestion of foods containing GLUTEN, such as wheat, rye, and barley. It is characterized by INFLAMMATION of the SMALL INTESTINE, loss of MICROVILLI structure, failed INTESTINAL ABSORPTION, and MALNUTRITION.Jejunum: The middle portion of the SMALL INTESTINE, between DUODENUM and ILEUM. It represents about 2/5 of the remaining portion of the small intestine below duodenum.Intestinal Absorption: Uptake of substances through the lining of the INTESTINES.Syndrome: A characteristic symptom complex.Lactose Intolerance: The condition resulting from the absence or deficiency of LACTASE in the MUCOSA cells of the GASTROINTESTINAL TRACT, and the inability to break down LACTOSE in milk for ABSORPTION. Bacterial fermentation of the unabsorbed lactose leads to symptoms that range from a mild indigestion (DYSPEPSIA) to severe DIARRHEA. Lactose intolerance may be an inborn error or acquired.