Specific types of diabetes
Key points
  • Diabetes mellitus is a severe chronic disease that occurs in the production of insulin by the body, or a violation of its effective use against the background of sufficient production. There are 3 main types of diabetes mellitus: type 1 diabetes mellitus, type 2 diabetes mellitus and gestational diabetes mellitus.
  • Type 1 diabetes most often occurs in childhood but can occur at any age. At this time, it cannot be prevented. People with type 1 diabetes can only live full lives with an uninterrupted supply of insulin, sufficient awareness, support, and the availability of blood glucose testing equipment.
  • Type 2 diabetes mellitus accounts for the vast majority (about 90%) of diabetes worldwide. It is possible to effectively influence its occurrence and course through education, support and adoption of a healthy lifestyle in combination with medication, if necessary.
  • "Prediabetes" is a term that is increasingly used for people with impaired glucose tolerance and / or with impaired fasting glucose. It determines the risk of future development of type 2 diabetes and diabetes-related complications.
  • Pregnant women with gestational diabetes may have high blood sugar, blood pressure, and high birth weight in babies as a result of gestational diabetes, which increases the risk of pregnancy and childbirth complications for both mother and baby.
The recently published WHO Diabetes Classification Report 2019 lists a number of "other specific types" [of diabetes], including monogenic diabetes and what was once called "secondary diabetes."

Monogenic diabetes, as the name suggests, is the result of a single gene and not the contribution of several genes and environmental factors, as seen in type 1 and type 2 diabetes. Monogenic diabetes is much less common, accounting for 1.5–2% of all cases, although this may well be underestimated. It is often misdiagnosed as type 1 or type 2 diabetes.

These monogenic forms have a wide spectrum, ranging from neonatal diabetes mellitus (sometimes referred to as "monogenic childhood diabetes"), young adult diabetes (MODY), and rare diabetes-associated syndromes. Although rare, they can serve as "human knockout models" to understand the pathogenesis of diabetes. From a clinical point of view, an accurate diagnosis of monogenic forms of diabetes is important, since in some cases the therapy can be adapted to a specific genetic defect. The further distinction between the fourteen different subtypes of MODY leads not only to differences in clinical management, but to different prognosis for the risk of complications. In recent years, with the accumulation of genome-wide genetic studies, an increasing number of monogenic forms of diabetes have been discovered, so the true prevalence of these types may be underestimated.

Newly diagnosed cases of diabetes that cannot be assigned to any of the categories described in this chapter are referred to as "unclassified diabetes."
Diabetes can also occur as a consequence of other conditions.
According to the WHO's latest classification for diabetes, these other types of diabetes are listed below.
Other specific types of diabetes
  • Diabetes mellitus caused by exocrine pancreatic diseases such as pancreatitis, trauma, infection, pancreatic cancer, and pancreatectomy
  • Diabetes mellitus due to endocrine disorders that cause excessive secretion of hormones that antagonize insulin
  • Diabetes caused by drugs and chemicals from medications that interfere with insulin secretion or its action
  • Diabetes caused by a viral infection associated with the destruction of beta cells
  • Unusual specific forms of immune-mediated diabetes (e.g., immunological disorders other than those that cause type 1 diabetes)
  • Other genetic syndromes sometimes associated with diabetes (i.e., Prader-Willi syndrome, Down syndrome, Friedreich's ataxia)