Those who have diabetes mellitus or who are aware of the disease may only know of two types: type 1 and type 2. However, some may be interested to learn that there is a third type, which is commonly called type 3c or Diabetes of the Exocrine Pancreas. This type of diabetes is caused by damage to the pancreas. A study found that this type of diabetes was commonly misdiagnosed by doctors as type 2.