The terms “Congenital Sucrase-Isomaltase Deficiency (CSID)” and “Genetic Sucrase-Isomaltase Deficiency (GSID)” are exactly equivalent in every regard. GSID and CSID refer to the same disorder. The term “congenital” means present at birth, and most congenital disorders are identified in infancy or early childhood. In recent years, many patients with CSID have been diagnosed in their teens or adulthood. CSID shares the same symptoms as many other gastrointestinal disorders, therefore, patients may have been misdiagnosed simply because they were not tested for CSID. Since the term “congenital” points to an early childhood diagnosis, it is more accurate to call a disorder involving deficient sucrase activity Genetic Sucrase-Isomaltase Deficiency. The term Genetic Sucrase-Isomaltase Deficiency implies that the disorder may be diagnosed in infancy, in childhood, in teenage years or in adulthood.