[Diabetes mellitus, but which type?].

In three patients with an unusual presentation of diabetes mellitus, the classification of their diabetes was troublesome. An adolescent male with slightly elevated blood-glucose levels turned out to have excellent glycaemic control on sulphonylurea derivatives only. When he was 40 years of age, his diabetes was finally diagnosed as 'maturity onset diabetes of the young' (MODY). A non-obese 41-year-old man was initially diagnosed with type-2 diabetes. Therapy with oral hypoglycaemic agents was unsuccessful and he was subsequently classified as having 'latent autoimmune diabetes of adults' (LADA) based on the presence of antibodies against glutaminic acid decarboxylase. A 29-year-old man presented with severe ketoacidosis and was initially believed to have type-1 diabetes. The patient himself discontinued insulin therapy and he was eventually diagnosed as having type-2 diabetes. A careful classification may have clinical consequences. Patients with MODY3, for example, respond to sulphonylurea derivatives. In MODY2, treatment with diet alone is often sufficient. In patients with LADA, insulin therapy is the treatment of choice. The recognition of diabetes mellitus type 2 as the underlying illness in some patients who present with ketoacidosis means that these patients can be specifically treated for their basic problem, which is insulin resistance. For them, weight reduction is essential and metformin is the drug of choice as far as pharmacotherapy is concerned, but of course attention must also be given to cardiovascular risk factors such as hypertension and dyslipidaemia.