Disaccharidase deficiency is a condition characterized by the insufficient activity of disaccharidase enzymes in the small intestine. These enzymes are crucial for the breakdown of disaccharides into monosaccharides, which are then absorbed into the bloodstream. Common disaccharidases include lactase, sucrase, and maltase. A deficiency in these enzymes can lead to various gastrointestinal symptoms when disaccharides are ingested.