Childhood Inherited Pancreatic Disorders
About Pancreatic Disorders
There is an extremely wide spectrum of inherited pancreatic disorders in childhood. Depending on the condition symptoms can develop at any time from birth to adulthood. The pancreas makes more than 25 different digestive enzymes which are secreted into the intestine to break down dietary protein, fat and starches into simpler molecules so that they can be absorbed. In fact, the pancreas has a tremendous reserve capacity – more than 95% of the function of the pancreas must be lost before the pancreas fails and symptoms of bloating and maldigestion develop. Children with digestive problems due to failure of the pancreas have to take enzyme replacement therapy with meals as well as additional fat soluble vitamins. The large pancreatic reserve also means that children can have a severe pancreatic problem without experiencing any problems with digestion.
The exocrine pancreas is not fully developed at birth. In fact, all healthy infants show some degree of maldigestion due to the fact that the pancreas is immature and does not have the same ability to produce enough enzymes. This is particularly true for starch and fat digestion. However, the pancreas matures after birth and by two years of age it is functioning in the same way as an adult pancreas. The immature pancreas appears to have no adverse effects on healthy children, but can have a major impact when children become malnourished or very ill.
Cystic fibrosis (CF)
Cystic fibrosis (CF) is, by far, the most common inherited pancreatic disease of childhood. It accounts for about 90% of childhood onset pancreatic disorders. CF affects many other organs as well and the most common cause of poor health and death is due to progressive lung disease. The CF pancreas begins to get damaged when the affected child is still in the mother’s womb. The small tubes inside the pancreas which allow digestive enzymes to reach the intestine get blocked with mucus and protein and the pancreas became badly scarred and shrinks. Many children with CF have evidence of severe pancreatic failure immediately following birth, and by two years of age 90% of CF are diagnosed – usually with severe malnutrition. Approximately 85% of all people with CF have pancreatic insufficiency and need to take pancreatic enzymes with meals. A lot is known about the genetic cause of CF. The CF gene, which is on chromosome 7, was identified in 1989. The most common CF-disease causing genetic mistake in this gene is called DF508, and is identified in approximately 70% of CF chromosomes worldwide. However, there are more than 1000 additional genetic mistakes in the CF gene, many of which are extremely rare. A lot of research is being done to try to correct the genetic disorder with gene therapy, and to discover ways of getting round the genetic disorder using special drugs.
Shwachman Diamond syndrome (SDS)
Shwachman Diamond syndrome (SDS) is the next most common inherited cause of pancreatic failure in childhood. It is much less common than CF and accounts for about 5% of inherited causes of pancreatic disease. This condition also affects other organs including the bone marrow (which makes blood cells), the skeleton and the liver. Children with SDS are very short and are at risk of experiencing severe infections and a particularly severe form of leukemia. Unlike CF, the gene that is responsible for SDS has not yet been identified. However, recent research shows that the SDS gene is also located on chromosome 7. The pancreatic problem is quite different from CF. The cells that make enzymes (acinar cells) don’t develop properly.
Other Inherited Pancreatic Diseases
After CF and SDS, other causes of inherited pancreatic disease are extremely rare. They include Johansson Blizzard syndrome, Pearson’s bone marrow syndrome and hereditary pancreatitis. It is interesting to note that the hereditary pancreas gene is on chromosome 7 as well. This is a coincidence!
In extremely unusual circumstances a child may be born without any pancreas – which includes both the digestive (exocrine) and insulin producing (endocrine) components of the pancreas.
Peter R. Durie, M.D., FRCPC
Professor, Department of Pediatrics
University of Toronto
Division of Gastroenterology/Nutrition
Head, CF Research Group, The Research Institute
The Hospital for Sick Children