What is Congenital Sucrase-Isomaltase Deficiency (CSID)?
CSID is an inherited metabolic disease characterized by a complete or almost complete lack of sucrase and a deficiency of isomaltase actvity. In the absence of sucrase and isomaltase activity, ingested sucrose (sugar) and isomaltose (type of starch) are not broken down and cannot be absorbed in the gastrointestinal tract. This results in an accumulation of undigested sugars in the intestine.
What are the symptoms?
Undigested sugars that accumulate in the intestine are responsible for watery diarrhoea, abdominal cramps, flatulence, bloating and vomiting.
The severity of symptoms depends on
• the quantity of sugar consumed and its effect on the colonic bacterial activity
• the absorptive capacity of the colon
• other mechanical factors
The symptoms can significantly impair the patients’ quality of life and might result in severe cases in failure to thrive.
Breast fed babies or infants consuming lactose-containing formulas will not manifest symptoms until sucrose is introduced into the diet in the form of fruit juices, solid foods and some medications. In young infants, passage of carbohydrate content through the small intestine and colon is faster than in adults leading to more severe symptoms. Intolerance to sucrose usually improves with age and symptoms of starch intolerance often disappear within the first few years of life. The enzyme deficiency does not change with age but patients become more tolerant to the condition.
Diagnosis and treatment
Diagnosis can be very long as many of the symptoms are common in several other diseases. Patients may be misdiagnosed with irritable bowel syndrome, cow's milk or soy protein allergy, cystic fibrosis or coeliac disease. Many patients remain undiagnosed.
A sucrose-free diet is very difficult to follow as large quantities of sugars are frequently found in cereals, soft drinks, baked goods and many other products including medications.
The deficiency of sucrase activity can be treated by replacing the missing enzyme enabling the products of sucrose hydrolysis, glucose and fructose to be absorbed. Patients are able to consume a normal sucrose-containing diet without experiencing gastrointestinal symptoms. This has an enormous impact on their quality of life. |
