Discovering Genetic Sucrase-Isomaltase Deficiency (GSID)

The digestive enzymes, sucrase and isomaltase assist in an individual’s ability to digest certain sugars. The absence or low levels of these two enzymes disrupts the digestive process, and can cause symptoms upon eating food containing sugars. This rare disorder is called Genetic Sucrase-Isomaltase Deficiency (GSID) and is equally prevalent in males and females. This disorder is also known as SI Deficiency, Disaccharide Intolerance, and Congenital Sucrase-Isomaltase Deficiency (CSID).

Sucrase deficiency can also occur due to other disorders, including those that cause irritation or inflammation of the intestinal lining, such a celiac disease or infection. In these cases, the sucrase level should return to normal once the primary cause is resolved and doesn’t require the same type of treatment as GSID. However, for patients with GSID, the deficiency is caused by a variation in the person’s genetics and will likely always be present.

The function of the sucrase enzyme is to aid in the breakdown of sucrose (table sugar) into its two sub-parts, glucose and fructose, which are then used by the body as fuel. This enzyme is produced in the small intestine. Isomaltase is the enzyme that helps the body digest starches. The individual’s inability to breakdown and absorb dietary sucrose and starch may impact the absorption of other nutrients and the hormonal regulation of gastrointestinal function. Unabsorbed carbohydrates affect gastric emptying, accelerates small-intestinal transit and they also contribute to malabsorption of starch, fat, and monosaccharides.

Patients suffering with Genetic Sucrase-Isomaltase Deficiency (GSID) are at risk of chronic malnutrition, diarrhea, gassiness, abdominal distention, and pain. Failure to thrive is another characteristic of this disorder.