The Evolving Sub-Types of Diabetes

Health Writer

Diabetes used to be framed in somewhat simple terms. Type 1 diabetes was considered “juvenile diabetes” because it typically started in youth, and it was identified as likely being caused by an autoimmune process. Type 2 diabetes used to be called "adult-onset" diabetes because it developed usually in midlife and was associated with poor lifestyle habits that instigated insulin resistance.

But the landscape of diabetes has changed and people are often diagnosed with a combination of types - such as type1/type 2 mixed, or a specific subtype. It's crucial for patients and doctors to recognize the specific type of diabetes a patient has in order to achieve maximal blood sugar control and a better long-term prognosis.

A study published in Diabetes Care reviewed primary care records of more than 2 million patients in England, analyzing the frequency of different types of diabetes diagnoses and how accurate the diagnosis was. Of particular interest was how often diabetes subtype 3c was identified.

Diabetes type 3c is a more recently recognized subtype of diabetes. The condition occurs as a result of inflammation of the pancreas (the organ that secretes insulin), abnormal growth of tissue on the pancreas, or surgical removal of part, or all, of the pancreas. The net result is diminishing or absent levels of insulin.

In this study, the researchers found that nearly 97.3 percent of individuals who had experienced some pancreatic disease were misdiagnosed as having diabetes type 2 rather than type 3c. The misdiagnosis meant that these patients received less-than-optimal treatment protocols, and most notably, did not receive insulin therapy quickly enough. Delays in receiving insulin can raise the risk of developing diabetes complications including eye, nerve, and kidney damage.

The researchers were also surprised to find that adults were more likely to develop type 3c diabetes, when compared to rates of type 1 diabetes. Among the subjects, 205 more people were newly diagnosed with type 3c diabetes than type 1. These findings suggest that there could be an escalating public health problem here in the United States as well - if indeed type 3c diabetes is being underdiagnosed.

Type 1.5 diabetes is another subset of diabetes. Also known as latent autoimmune diabetes in adults (LADA), the condition is a form of type 1 diabetes that has some features more commonly associated with type 2 diabetes. For that reason it is sometimes identified as a hybrid form of diabetes. Type 1.5 diabetes is usually diagnosed in adulthood and has a slower onset, similar to type 2 diabetes. Unlike type 2 diabetes, this subset is an autoimmune disease and therefore similar to type 1 diabetes. Once an individual develops type 1.5 diabetes, the likelihood is that insulin use will be necessary at some point. Type 2 diabetes is often responsive to lifestyle change and especially to weight loss if obesity is present.

Type 1.5 is often misdiagnosed as type 2 diabetes and, in fact, as many as 15 to 20 percent of people diagnosed with type 2 likely have type 1.5 diabetes. Type 1.5 diabetes is not usually responsive to treatments that attempt to improve insulin resistance. That’s because individuals with type 1.5 have little or no resistance to insulin. They also don’t typically have metabolic syndrome, a cluster of diagnostic findings and conditions that usually accompany type 2 diabetes.

Similar to type 1 diabetes, type 1.5 is caused by factors outside of the patient's control. The process is somewhat similar to the autoimmune process responsible for type 1 but occurs at a much slower pace. Some experts believe that LADA, or type 1.5 diabetes, is simply a "slower-occurring type 1 diabetes."

If you have been diagnosed with type 2 diabetes and you are not responding to lifestyle changes, or you are lean and physically active or have recently lost weight while still showing signs of diabetes, ask your doctor to test you for type 1.5 diabetes. This would include a screening for antibodies. If you have any history of pancreatic inflammation or disease and develop diabetes, then type 3 diabetes should be a strong consideration.

It’s also worth a quick mention that Alzheimer’s disease has also been called “type 3 diabetes” because some of its pathogenesis is due to insulin resistance in the brain. Researchers have known for some time that people who experience insulin resistance have an increased risk of developing Alzheimer’s disease.

See more helpful articles:

Type One-and-a-Half Diabetes

What’s the Risk of Type 1 or Type 2 or Type 1.5?

What is Type 3 Diabetes?