Congenital Sucrase-Isomaltase Deficiency (CSID) is an inherited enzyme deficiency disorder that affects a person’s ability to digest sucrose (table sugar) and starch. The prevalence of CSID is estimated to be between 1/500 and 1/2 000 among individuals of European descent. The condition is more prevalent in the native populations of Greenland, Alaska, and Canada, where as many as 1 in 20 people may be affected.
CSID can cause symptoms similar to Irritable Bowel Syndrome (IBS)
The intestinal enzyme sucrase-isomaltase (SI) is expressed in the brush border membrane of the small intestine, and aids in the breakdown of sucrose and starch into glucose and fructose. Patients with CSID have a mutation in the SI gene that results in lack of and/or impaired function of the SI enzyme. This leads to malabsorption and the sugar being fermented by the intestinal flora, which can cause symptoms similar to IBS, like diarrhea and abdominal pain, but also poor weight gain and failure to thrive.
CSID is a hereditary enzyme deficiency disorder
CSID is an autosomal recessive disease, which means that a person needs to inherit a mutated SI gene from both parents to develop the disorder. The SI gene is located on chromosome 3 and may be mutated in different ways. At present, more than 25 mutations in the gene responsible for the synthesis of SI have been discovered and about 80% of patients have at least one of the four most common mutations. These mutations result in a variety of defects and is reflected in a range of enzymatic capability ranging from completely absent activity to low but present residual activity.
Chronic diarrhea and abdominal pain are common symptoms of CSID
The symptoms of Congenital sucrase-isomaltase deficiency can vary between individuals, but usually becomes apparent after an infant is weaned and starts to consume fruits, juices, and grains. After ingestion of sucrose or maltose, an affected child will typically experience diarrhea, stomach cramps, bloating and excess gas production. These digestive problems can lead to malnutrition, failure to gain weight and grow at the expected rate (failure to thrive). Studies show that even carriers of just one mutated copy of the SI gene can experience symptoms