Unusual Case of Autoimmune Diabetes Mellitus in the Setting of Extra-Adrenal Paraganglioma with Loss of Succinate Dehydrogenase Expression

ABSTRACT Objective: To report a case of a catecholamine-secreting paraganglioma with possible tumor-dependent autoimmune diabetes mellitus. Methods: We present the imaging, laboratory, and pathologic findings and describe the clinical course of a patient with a norepinephrine-secreting aortic paraganglioma with succinate dehydrogenase deficiency who was concomitantly diagnosed with latent autoimmune diabetes of adults at the time of initial diagnosis. We performed immunohistochemistry on the paraganglioma tissue for glutamic acid decarboxylase-65 (GAD65). Results: A 55-year-old man was diagnosed with a retroperitoneal, norepinephrine-secreting paraganglioma. He was concomitantly found to have elevated serum glucose levels and positive anti-GAD65 antibodies, consistent with latent autoimmune diabetes of adults, and was started on a basal-bolus insulin regimen. Surgical removal of the tumor resulted in rapid improvement of his hypertension and glycemic control, eliminating the need for insulin therapy within 6 months. Approximately 18 months after surgery, he presented with worsening glycemic control, unintentional weight loss, and hypertension. His anti-GAD65 antibody titer increased dramatically compared to the initial evaluation, and imaging and lab results were consistent with recurrence of the paraganglioma with metastatic spread. Immunohistochemistry for GAD65 in the original paraganglioma tissue was negative. The patient is currently undergoing cytoreductive therapy, and his diabetes is well-controlled on basal-bolus insulin therapy. Conclusion: Paragangliomas can induce hyperglycemia through several mechanisms. However, here, we present a unique case of autoimmune diabetes in the setting of a paraganglioma, whose severity of hyperglycemia and autoimmune antibody titers appear to follow the timeline of paraganglioma treatment and recurrence, raising suspicion for a paraneoplastic syndrome. Abbreviations: CT = computed tomography; GAD65 = glutamic acid decarboxylase-65; IHC = immunohistochemistry; LADA = latent autoimmune diabetes of adults; SDH = succinate dehydrogenase