A random finding of hyperglycaemia in children and adolescents is a good reason for detailed evaluation and for estimation of the underlying disorder. Hyperglycaemia may be the first sign of an early phase of type 1 diabetes mellitus, of type 2 diabetes mellitus, of a diabetic syndrome or of a subtype of MODY diabetes (Maturity-Onset Diabetes of theYoung). These conditions differ by their natural course, long-term prognosis and by optimal therapy.

        Key words: hyperglycaemia, children, type 1 diabetes mellitus, type 2 diabetes mellitus, diabetic syndromes, MODY, diagnostic approach, molecular genetics