INS and myotonic dystrophy type 2: In contrast to DM2, a small number of monogenic defects have been recognized to cause the uncommon autosomal dominantly inherited forms of maturity-onset diabetes of the young (MODY).23 These defects disrupt β-cell function, and their recognition and precise genetic diagnosis is clinically important in directing treatment towards more effective and easier-to-use sulfonylurea drugs rather than insulin.