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Awareness of Type 3C Diabetes and Why It Is Misdiagnosed

Diabetes has long been divided into type 1 and type 2. But a third type has entered the mix — and we aren’t diagnosing it correctly.

Type 1 diabetes occurs when the pancreas doesn’t produce insulin and is usually diagnosed at a young age. Type 2 diabetes shows up later in life when the pancreas can’t make enough insulin to keep up with the body. This new third type, Type 3c, starts with a damaged pancreas.

The researchers say that pancreatitis is leading to misdiagnoses of type 2 diabetes in people who actually have type 3c diabetes.  A new study involving two million people has found 97.3% of those who had previously suffered from pancreatic disease (acute pancreatitis or chronic pancreatic disease) had been wrongly diagnosed with type 2 diabetes when, in fact, they actually had type 3c diabetes, despite a sevenfold increased insulin requirement within 5 years, by which time 45.8% of patients with diabetes following chronic pancreatic disease are using insulin.

Type 3c diabetes, also known as pancreatogenic diabetes, is not as well known compared to type 1 and type 2 diabetes.  It develops when the pancreas becomes inflamed, or part of it is removed and eventually stops producing insulin.

A recent study from the American Diabetes Association found only 3 percent of people with type 3c have actually received a correct diagnosis. These misdiagnoses mean people with type 3c might not be getting effective treatments. People diagnosed with type 3c require insulin, but may also benefit from taking digestive enzyme tablets, one of the study’s researchers wrote. That alternative treatment option is what sets type 3c apart from the other types.

Correctly identifying the type of diabetes is important as it helps the selection of the correct treatment. Several drugs used for type 2 diabetes, such as gliclazide, may not be as effective in type 3c diabetes. Misdiagnosis, therefore, can waste time and money attempting ineffective treatments while exposing the patient to high blood sugar levels.

Because type 3c diabetes is often misdiagnosed, the first large scale population study to try to find out how common type 3c diabetes is and just how well patients’ diabetes is controlled was just finished.  So, to accomplish this they analyzed health records from over 2 million people. To the surprise of the researchers, they found that in adults, type 3c diabetes was more common than type 1 diabetes. We found that 1% of new cases of diabetes in adults were type 1 diabetes compared with 1.6% for type 3c diabetes.

People with type 3c diabetes were twice as likely to have blood sugar levels that were unhealthy than those with type 2 diabetes. They were also five to ten times more likely to need insulin, depending on their type of pancreas disease. They found that the onset of type 3c diabetes could occur long after the onset of pancreas injury; in many cases more than a decade later. This long lag may be one of the reasons the two events are not often thought of as being linked, and the diagnosis of type 3c diabetes is being overlooked.

Correctly identifying the type of diabetes is important as it helps the selection of the correct treatment. Several drugs used for type 2 diabetes, such as gliclazide, may not be as effective in type 3c diabetes. Misdiagnosis, therefore, can waste time and money attempting ineffective treatments while exposing the patient to high blood sugar levels.

Recognizing the role of pancreatic damage in the development of a patient’s diabetes is vital to inform appropriate management plans. In diabetes of the exocrine pancreas, the production of insulin is usually reduced. This is caused by β-cell dysfunction following pancreatic inflammation or by absolute β-cell loss. In addition, pancreatic polypeptide upregulates insulin receptor expression in the liver, and its loss can lead to hepatic insulin resistance, an important physiological difference between diabetes of the exocrine pancreas and type 1 diabetes. Glucagon production from pancreatic α-cells is also diminished, which may explain the episodes of severe hypoglycemia that are reported in some patients. Failure to recognize this altered physiology may result in suboptimal treatment. Newer incretin-based agents, such as glucagon-like peptide 1 receptor agonists (“incretins”) and dipeptidyl peptidase 4 inhibitors (“gliptins”), would usually be considered contraindicated because of the presence of pancreatic damage. Insulinopenic patients with diabetes of the exocrine pancreas could be unfairly labeled as poorly compliant if they are misclassified as type 2 diabetes and show resistance to oral antihyperglycemic agents. Malabsorption secondary to pancreatic exocrine dysfunction is common, and pancreatic enzyme and vitamin D replacement is required to prevent malnutrition and osteoporotic bone disease.

In summary, diabetes that develops following pancreatic disease is significantly associated with poor glycemic control and early insulin therapy but is rarely identified as diabetes of the exocrine pancreas. Clinicians should elicit whether a patient has any history of pancreatic disease when they first present with diabetes and consider the diagnosis of diabetes of the exocrine pancreas. Diabetes of the exocrine pancreas must be appropriately recognized to tailor management, including choice of antihyperglycemic therapy, and consideration of malabsorption requiring pancreatic enzyme and vitamin D prescription. Greater awareness of diabetes of the exocrine pancreas is required to appropriately manage this diabetes subgroup.

The findings highlight the urgent need for improved recognition and diagnosis of this surprisingly common type of diabetes.  Thus, researchers hope this new study can stress the prevalence of this disease and encourage its proper diagnosis.

Practice Pearls:

  • Diabetes following pancreatic disease has a higher incidence in adults than type 1 diabetes.
  • Diabetes that develops following pancreatic disease is significantly associated with poor glycemic control.
  • Recognizing this new form of diabetes will improve the treatments and improve the quality of life for those patients diagnosed with type 3c diabetes.

Reference:

Diabetes Care 2017 Nov; 40(11): 1486-1493. https://doi.org/10.2337/dc17-0542