Post-Thymectomy Autoimmune Flare-Up With New-Onset Type 1 Diabetes Mellitus

The thymus gland aids in the maturation of the immune system. An overactive or malfunctioning thymus gland, as seen in thymomas, can lead to disrupted immune systems. Thymectomy, the usual treatment, can paradoxically lead to further derangements in the immune system, leading to new autoimmune disorders. Most of these reported disorders are rheumatological. Except preclinical studies, there are no reported cases of autoimmune diabetes post-thymectomy. A 25-year-old woman who had malignant thymoma underwent chemotherapy, followed by thymectomy and radiotherapy. She developed autoimmune diabetes mellitus (AID) approximately 1 year post-thymectomy, evident from raised glycated hemoglobin, anti-glutamic acid decarboxylase (GAD) antibodies, ineffectiveness of oral glucose-lowering agents, and positive response to insulin. AID can occur after thymectomy, as evidenced by animal studies and this case report. Whether these patients would have long-term outcomes and control of diabetes differently than classic type 1 diabetes mellitus (T1D) is uncertain. Further research is needed to prove causality between thymectomy and diabetes.