Rare types of diabetes mellitus.

Diabetes mellitus is a heterogenous disorder characterized by chronic hyperglycemia and induced by a large number of etiopathogenic conditions. Beside type 1 and type 2 diabetes, which account for almost 90% of all cases, practitioners may encounter patients with more infrequent forms of diabetes, as those induced by mutations of a single gene, atypical immune disorders or neonatal diabetes. Monogenic diabetes is represented by genetic disorders in the structure of the beta-cell (the MODY syndromes and the mutations of mitochondrial DNA) or in the insulin's action (type A insulin resistance syndrome, Rabson-Mendenhall syndrome, leprechaunism, lipodystrophies). The rare forms of immune diabetes are determined by antibodies against insulin or insulin receptor or appear as a component of the "stiff man syndrome". Neonatal diabetes is induced by mutations in genes that control beta-cell development and function and may have a transient or permanent nature. Knowledge of the uncommon forms of diabetes mellitus enables physicians to apply the optimal treatment, to estimate the evolution of the patient and to apply a complete family screening in order to diagnose all other blood relatives as soon as possible.