Individuals with congenital sucrase-isomaltase enzyme deficiency cannot break down the sugars sucrose (table sugar) and maltose (found in grains) in the small intestine. The deficiency is caused by several possible genetic mutations, the main ones being SI and SII. Depending on the mutation, sucrose, starch and sometimes lactose are tolerated to varying degrees. Inheritance is by an autosomal recessive pattern, i.e. both parents must have the mutation for the child to develop the disease. The parents (heterozygotes) typically do not show signs and symptoms of the condition.
Frequency in population and natural history
- Frequency estimated to be 1 in 5,000 people of European descent. In native populations of Greenland, Alaska, and Canada up to 1 in 20 individuals may be affected
- In pediatric patients with chronic diarrhea of unknown origin 4-10% had sucrose-isomaltase deficiency
- 1 in a 1000 patients with diarrhea have some degree of SI deficiency
- Between 2 and 9% of the general US population are carries of the genetic abnormality (heterozygotes) without significant symptoms
- Congenital sucrase-isomaltase deficiency usually becomes symptomatic after an infant is weaned and starts to ingest fruits, juices, and grains. Children may tolerate sucrose and maltose better as they get older. The disease can however persist or, even more rarely, appear in adulthood. If the diet is restricted appropriately affected individuals live normal lives.
The ingestion of sucrose, maltose or starch typically results in stomach cramps, bloating, excess gas production, nausea, vomiting and diarrhea. Upper respiratory tract and viral infections are common. These digestive problems can lead to lower than normal weight gain and growth. Possible associations are kidney stones and copper malabsorption.
Testing and diagnosis
Genetic analysis or enzyme activity determination in small intestinal biopsies, (possible in our clinic) and the C13-sucrose breath test are the most accurate diagnostic tools. Sucrose breath hydrogen breath tests are simple and useful, but less accurate.
Avoidance of sucrose and maltose intake is required. This means avoiding table sugar in all forms, such as sugar cane and sugar beets, sorghum, confectioners' sugar or powdered sugar, rock candy, brown sugar (made of white sugar and molasses), cotton candy, maple syrup, Demerara and Barbados sugar, molasses, pancake syrup, gingerbreads, baked beans and pumpernickel breads.
In those with prominent starch intolerance, sources of starch need to be avoided as well.
Sacrosidase (Sucraid®) is the appropriate oral enzyme replacement (Orphan Medical, Inc, USA) for sucrose digestion, but not for maltose.
See Food tables for a listing of sucrose, starch and maltose content in food.
Links to literature
Symposium review papers on sucrose-isomaltase deficiency from the 8th Starch Digestion Consortium Workshop in the JPGN 2012;55:Supplement 2