The digestive system is constituted by all the organs related to digesting food - the mouth, the esophagus, the stomach, the liver, the biliary tract, the pancreas, the small and large bowels. In Bloom's syndrome, all these organs have developed normally it seems, but there are perturbations of normal function. Persons with Bloom's syndrome exhibit a remarkable disinterest in food. In early life, there is more vomiting and diarrhea than normal. Throughout life, persons with Blooms syndrome have more problems with gastroesophageal reflux, a condition in which recently ingested food is belched back up the esophagus, along with the digestive stomach acids, which can damage the esophagus and, if aspirated, the lungs as well.
One function of the digestive system is to digest and metabolize food. In Bloom's syndrome, a poorly understood metabolic defect is present. One manifestation of this metabolic defect is the increased frequency of diabetes in persons with Bloom's syndrome. Diabetes is defined as excess sugar in the blood. It is caused by problems with sugar metabolism. After a meal, the food is processed and absorbed in the gut and sugars are released into the blood stream for cells to use as a source of energy. In order for the cells to process and use the sugars, they need insulin. A subset of cells in the pancreas produce insulin and secrete it into the blood stream in response to sugar levels in the blood. If insulin is not properly produced or processed, then sugar levels remain high in the bloodstream. High sugar levels can damage many different organs, including the heart, blood vessels, eyes, kidney, the gums, and nervous system.
As noted, diabetes and abnormal sugar metabolism is more common in persons with Blooms syndrome than in normal persons. Insulin is produced in response to sugar but in some persons with Bloom's syndrome the sugar levels remain higher longer and the amount of insulin can be higher than normal too. The cells that produce insulin are maintained by a stem cell* population in the pancreas. Might these cells be challenged in maintaining their numbers and proliferation capacity?
Fats are also absorbed from food. Persons with Bloom's syndrome have a paucity of sub-cutaneous fat. Parenteral feeding has in some instances resulted in increased body weight, suggesting that the lack of body fat could be dependent on the lack of interest in food; however, clinical studies suggest that this is not the whole story and that metabolism of fats is also defective.
*For more information about stem cells, please see Small Body Size.