Glucagonoma syndrome is a rare paraneoplastic phenomenon, with an estimated incidence of one in 20 million, characterized by necrolytic migratory erythema, hyperglucagonemia, diabetes mellitus, anemia, weight loss, glossitis, cheilitis, steatorrhea, diarrhea, venous thrombosis and neuropsychiatric disturbances in the setting of a glucagon-producing alpha-cell tumor of the pancreas. The gene discussed is GCG; the disease is diabetes mellitus.