Congenital sucrose-isomaltase deficiency (CSID) is an autosomal recessive disorder characterized by absence of sucrase and most of the maltase digestive activity within the sucrase-isomaltase enzyme complex, with the isomaltase activity varying from absent to normal. The large amounts of unabsorbed disaccharides create osmotic-fermatative diarrhea with symptoms such as vomiting, flatulence, and abdominal pain (summary by Sander et al., 2006).