Monogenic diabetes is a term used to describe a group of single-gene causes of diabetes. Traditional nomenclature has focused on the types of diabetes known as MODY, defined as maturity-onset diabetes of the young; infantile (or perinatal) onset diabetes, including permanent and transient neonatal diabetes mellitus; and syndromic types. These syndromes include genes associated with insulin resistance, such as the insulin receptor itself. A growing field is also focused on single gene variants that are responsible for multi-autoimmune syndromes that include type 1 diabetes. Altogether, monogenic diabetes may account for up to 3% of all diabetes diagnosed before age 35 years, amounting to an estimated 300,000 cases in the United States. However, a systematic study of incidence and prevalence in the United States has not been done.