Many a patient diagnosed with type 1 or type 2 diabetes responds poorly or hardly at all to the medication intended for it. There are many reasons, but one is particularly common: an incorrect diagnosis. Because type 3 diabetes is still simply forgotten. Some readers may have never even heard of type 3, although it is omnipresent in everyday clinical practice.
Yes, there is type 3 diabetes
Type 3 diabetes is a term that summarizes a heterogeneous group of diabetes diseases that cannot be classified into the classic type 1 or type 2 diabetes categories. Diabetes mellitus is known to be an epidemic metabolic disease characterized by chronically elevated blood sugar levels (International Diabetes Federation, 2021). Diagnosing type 3 diabetes can be challenging due to the multitude of variants and the diverse pathophysiology underlying these disorders. However, advances in genomics and proteomics offer new opportunities to improve the diagnosis of these disorders (Arya et al., 2020). Not least because of this, hardly anyone dares to leave the supposedly safe ground of the well-researched types 1 and 2. The fact that very different forms are subsumed under the umbrella term “type 3 diabetes” is not the problem. The inconsistent use of subtype assignment in the literature is harmful.
International conceptual chaos
There is agreement on the existence of type 3 diabetes, but when it comes to the distinctly different subtypes, definitional chaos reigns (Ahuja et al., 2021). For example, in the US literature, the term “type 3 diabetes” is mostly associated with Alzheimer’s disease, which – completely absurdly – is also called “type 3 diabetes” (de la Monte & Wands, 2008). This designation is based on the hypothesis that insulin resistance and impaired insulin signaling in the brain may contribute to the development of Alzheimer’s (Steen et al., 2005). Future research must focus on a better understanding of the pathophysiology of these diseases in order to develop improved diagnostic and therapeutic approaches. Until then, it is very important to take account of differences in definitions and naming in the international context in order to avoid misunderstandings and inconsistent classifications.
In Germany…
Currently, most German-language literature is categorized as follows:
Type-3a: Monogenetic Diabetes (MODY) Type 3a diabetes, also known as Maturity-Onset Diabetes of the Young (MODY), is a rare form of diabetes that is due to genetic defects that affect beta cell function (people-with-diabetes). Often confused with type 1.
Type-3b: This variant refers to diabetes caused by disease, damage, or loss of the pancreas, such as chronic pancreatitis, an autoimmune-induced loss of islet cells through to pancreasectomy.
Type-3c: Also pancreopriver diabetes (secondary acquisition) has to the core that those Pancreas is not able to provide enough insulin due to other diseases. The spectrum ranges from chronic alcohol intoxication to neoplasia, fibrosis, cystic fibrosis and iron storage diseases. This type is therefore relatively common.
Type-3d: Secondary diabetes, which occurs quite frequently, especially in the context of hormonal (endocrine) diseases and metabolic disorders. The spectrum is so wide that it is not listed here. In general, one should not immediately think of type 2 in endocrinologically ill people who develop diabetes in the course of the disease. Especially if the BMI is in the normal or gray range, the possibility of type 3 diabetes should always be considered.
Type-3e: The variant in which chemicals, toxins or drugs are the cause. For drugs and chemicals, mostly ‘curable’ by avoiding further exposure.
Type-3f bis 3g: Rare causes such as viral infections as well as genetic and autoimmune diseases, mostly orphan diseases.
Conclusion – what to do?
Type 3 diabetes represents a complex and diverse group of diseases that pose new challenges for both researchers and healthcare professionals. With a better understanding of the different variants and their pathophysiology, we can improve the diagnosis, treatment and prevention of these diseases. It is of utmost importance to consider the differences in the definitions and naming of type 3 diabetes in the international context to ensure consistent and effective communication between researchers and healthcare professionals.
With the growing prevalence of diabetes worldwide, it is high time that research in this area continued to better understand and treat both known and lesser-known diabetes diseases. Research into type 3 diabetes can help develop new therapeutic approaches tailored to the individual needs of patients and improve the lives of those affected by these diseases.
Take away
Not all diabetes is type 1 or type 2, especially in patients with other chronic pre-existing conditions, especially if the BMI is below 30. Type 3 diabetes should therefore always be kept in mind.
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