How to distinguish GSID from other gastrointestinal disorders
Many patients with GSID, also known as CSID, lack sucrase, the enzyme needed for sucrose digestion. An individual with GSID cannot digest sucrose, and therefore develops gastrointestinal (GI) symptoms after eating food containing sucrose. Many patients with GSID also have irregular amounts of the enzymes required for starch digestion (isomaltase, palatinase, maltase). These patients may experience gastrointestinal symptoms from starch consumption.
GSID patients may have gastrointestinal symptoms that range from mild to severe when dietary sucrose moves through the small intestine undigested. The undigested sugar enters the colon, where bacteria exist. The bacteria feeds off of the increased amount of sugar, and fermentation occurs. The results are increased gas production and diarrhea. When substances are not absorbed in the colon and retain water, osmotic diarrhea occurs. Symptoms may differ between infants, children, and adults.
Infants and Children
Symptoms of GSID, more commonly known as Congenital Sucrase-Isomaltase Deficiency (CSID), do not begin manifesting in infants until they begin to ingest sucrose- and starch-containing foods (e.g., juices, solid foods, formula, and medications sweetened with sucrose). Infants who are breastfed may not show symptoms until formula is introduced into their diet, or they begin eating solid foods. Chronic abdominal pain, watery diarrhea, and/or failure to thrive (poor physical growth) are common GSID symptoms. Abdominal swelling (distention), gassiness, colic, irritability, excoriated buttocks (abrasions and irritations), vomiting, and diaper rash are signs of pediatric GSID. When patients show signs of dehydration, malnutrition, muscle wasting, and weakness, hospitalization may be required. However, this occurs only in a minority of patients. Children’s symptoms may be more severe than adults because they have shorter GI tracts.
GSID is sometimes misdiagnosed in infants. They are thought to have chronic, nonspecific diarrhea (toddler’s diarrhea). Older children may be misdiagnosed with Irritable Bowel Syndrome (IBS) because they have symptoms such as cramps, abdominal pain, gas, and intermittent diarrhea. Unfortunately, patients may learn to live with their symptoms and are never properly diagnosed. Other mistaken diagnoses may include milk protein intolerance, food allergies, and chronic, nonspecific diarrhea. It is important to note that GSID is a genetic disease that patients do not “outgrow.”
Adult symptoms are similar to those of infants and children, but due to the fact that they have a longer GI tract than children, their symptoms may not be as severe. In adults, patients may “learn to live with” their gastrointestinal symptoms, and assume GI issues are “normal.” Recurrent symptoms like chronic diarrhea, unexplained abdominal pain, bloating, weight loss, frequent bowel movements, gassiness, abdominal distention, and vomiting should not be ignored. Symptoms in adults may vary. They may be limited to an increase in bowel frequency, abdominal distention, and flatulence, and episodic watery diarrhea may occur upon ingestion of high levels of sucrose. Also, diarrhea may alternate with constipation, which may lead to a misdiagnosis of Irritable Bowel Syndrome (IBS). Any recurring, persistent gastrointestinal symptoms should be discussed with a gastroenterologist.
Failure to absorb dietary sucrose and starch can impact the absorption of other nutrients, and the hormonal regulation of gastrointestinal function. If carbohydrates are not absorbed properly, it slows down gastric emptying and accelerates small-intestinal transit time. This in turn contributes to malabsorption of starch, fat, and monosaccharides. The severity of symptoms can be affected by contributing factors such as the quantity of sucrose and starch consumed, the colonic bacterial activity, the absorptive capacity of the colon, the rate of gastric emptying, and the small bowel transit time.