Type 2 diabetes in children and adolescents is on the increase, and affects children in both developed and developing nations. Many of these children risk developing diabetic complications at an early age, which would place a significant burden on the individual, national health budgets as well as society as a whole.

It is well recognized that the global burden of type 2 diabetes is both significant and rising, with most of the increase registered in the last two decades. The worldwide prevalence of diabetes in adults is expected to increase from 5.9% to 7.1% of the adult population from 2007 to 2025, or from 246 million to 380 million people (see Diabetes Prevalence and Projections). The largest proportional and absolute increases will occur in developing countries. In India and China, the number of adults with diabetes is expected to increase by 50-70% between 2007 and 2025 to reach 70 million in India and 59 million in China by 2025.

In 1990 it was estimated that 0.2% of the total global diabetic population of 118 million was under 15 years of age   1 . The prevalence of type 2 diabetes increases with age and affects some 17% of all 65-74 year olds in the USA, and a similar proportion in Australia   2   3   4 . Amongst the young, type 2 diabetes is thought to account for 2-3% of all types of diabetes. This however, may be an underestimate, as depending on the study, 8-45% of recently diagnosed diabetes in the young in the USA is due to type 2 diabetes   5 .

Compared to adults there is little information on type 2 diabetes incidence and prevalence in the young with many surveys being clinic based or case series with a paucity of population-based surveys, particularly outside North America   3 , Japan   6  and Taiwan   7 . Similarly, information on the natural history and aetiology of type 2 diabetes in the paediatric age range is also sparse. Other deficiencies include a lack of uniformity in case definition, data collection and follow-up, with the diagnosis often made retrospectively   8 .

There are, however, ever increasing reports of type 2 diabetes in children worldwide, with some as young as eight years of age being affected   9 . These are mostly in ethnic groups known to be at high risk of type 2 diabetes. There are now also reports of type 2 diabetes occurring amongst Europid (White Caucasoid) teenagers   10 . In Japan, the prevalence of type 2 diabetes amongst junior high school children has doubled from 7.3 per 100,000 in 1976-80 to 13.9 per 100,000 in 1991-95, with type 2 diabetes now outnumbering type 1 diabetes in that country   6 .

Despite the paucity of information, it is now becoming recognized that type 2 diabetes in children is becoming a global public health issue with potentially serious health outcomes   11 . In response to this the American Diabetes Association (ADA) has issued a consensus statement on the screening, diagnosis and treatment of children with type 2 diabetes   5 .

The impact of misclassification
There may be underestimation in type 2 diabetes rates due to a misclassification of the type of diabetes at initial presentation. The presence of diabetic ketoacidosis (DKA) is classically a manifestation of type 1 diabetes. However, a number of reports have shown that DKA may occur at initial presentation in people who are eventually found to have type 2 diabetes. That is, they have elevated C-peptide and an absence of islet cell or anti-GAD antibodies   3 . This type of presentation has also been termed Flatbush   12   13 , or atypical diabetes mellitus (ADM)   14 .

Unlike type 1 diabetes, most children with type 2 diabetes are asymptomatic. However, approximately a third present with ketonuria, an excess of ketones in the urine   15 . One study found DKA occurred in 4.2% of all patients attending their paediatric clinic, all of whom were of Canadian aboriginal descent   16 . A case series examining African Americans adolescents found that up to 42% presented with ketonuria and 25% with DKA   17 . Similarly another report has shown that some 30% of Hispanic youth with type 2 diabetes can present with ketosis   18 . Why type 2 diabetes can present with ketosis and in particular why this presentation is more likely to occur in African Americans or Hispanics is not clear   19 .