There is mounting evidence from experimental animal diabetes and from
human epidemiological studies that a long period of ''prediabetes'' pr
ecedes the clinical onset of type 1 (Insulin Dependent) Diabetes Melli
tus. In this review, the authors evaluate the main informations concer
ning the genetic, immunological and metabolic aspects of this phase of
prediabetes and the relationship of prediabetes with the onset of the
disease. Prediabetes is a long period; in this period the destruction
of beta cells can be caused by many factors and by many pathogenetic
mechanisms. Nowadays, we begin to understand some of these mechanisms
and the central role of the activation of the immune system; this acti
vation results in various humoral and cellular abnormalities detectabl
e in the prediabetic phase. These abnormalities, together with metabol
ic ones, have been reported in many studies. Consequently, we have at
our disposal some genetic, immunological and metabolical markers which
can be useful in the detection of the person at risk of developing di
abetes mellitus.