Classification of Diabetes Mellitus

4. Classification of Diabetes Mellitus

Different terminology has been used to describe the different forms of diabetes mellitus in humans and other species. The following terminology, based on the underlying pathophysiology, will be used throughout this chapter. Primary diabetes mellitus can be subdivided into type 1 diabetes mellitus (1DM) and type 2 diabetes (2DM) (Table 2).

In humans, these were formerly also named juvenile and adult-onset diabetes, respectively. However, due to the massive increase in childhood obesity, up to 50 % of diabetic children now suffer from 2DM compared to only 5 - 10% as observed previously. Therefore, the terms of juvenile or adult-onset diabetes should no longer be used.

Insulin-dependent (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM) are purely descriptive terms which define the necessity of a diabetic human or animal to be treated with insulin to achieve metabolic control. The underlying pathophysiology is not reflected in these terms and will therefore not be used here.

The most common type of feline DM is pathophysiologically similar to 2DM in humans (for review, see Henson & O’Brien, 2006) and will be described in the following paragraph. Even though 4-Classification of diabetes mellitus histological changes in pancreatic islets suggestive of a 1DM like syndrome have been described in cats (Nakayama et al., 1990), this seems to be an uncommon finding. Further, cats do not develop autoantibodies against beta-cell antigens or insulin (Hoenig et al., 2000), arguing against an autoimmune- induced form of diabetes typical for 1DM. Finally, it is now recognized that the pathophysiology of 2DM also involves inflammatory, immune-mediated processes (Donath et al., 2005). Therefore, the presence of inflammatory processes does not exclude a 2DM like pathophysiology.