LBODP100 A Rare Case Of Pembrolizumab Induced Graves’ Disease

Cancer immunotherapies have recently changed the therapeutic armamentarium of anti-cancer treatments, particularly for melanoma and cancers of the kidneys, lungs, and colon. Immune checkpoint inhibitors (ICPis) act on various immune checkpoints. Of them, anti-PD-1 antibodies (such as pembrolizumab) are monoclonal antibodies that act against programmed cell death 1 protein. However, by counteracting the regulators of adaptive immunity, this class of drugs may cause immune-related adverse events that involve multiple organs and endocrine glands, such as the thyroid gland. The symptoms of thyroid dysfunction usually present during the first weeks of ICPis therapy. In the current report, we present a case of a 50-year-old male who presented to the emergency department complaining of fever, chills, nausea, and vomiting for one week. The patient had a history of colon cancer with lymph node metastasis status post tumor resection and colostomy. He began Keytruda® (pembrolizumab) treatment after tumor resection, and the presenting symptoms appeared after receiving the first immunotherapy infusion. His medical history was significant for psoriasis and rheumatoid arthritis. The patient's history was unremarkable for thyroid diseases, and he did not receive thyroid medications with no previous exposure to intravenous contrast media, over-the-counter iodine preparations, or biotin. At the emergency department, the patient had a temperature of 101.4°F, a heart rate of 110 bpm, and blood pressure of 130/70 mm Hg. On examination, tenderness was indicated upon palpating the anterior part of the neck. The patient was treated with intravenous fluids, steroids, beta-blockers, and broad-spectrum antibiotics. A workup for sepsis was requested, and it revealed negative blood culture and urine culture results. His laboratory indices demonstrated a suppressed level of TSH (0. 01 mIU/mL) and elevated Free T4 (3.16 ng/dl). Still, his TSH level reported at the Oncology clinic before Keytruda administration was (0.9 mIU/mL), and Free T4 was (1.7 ng/dl). Thyroid ultrasound revealed a heterogeneous thyroid gland consistent with thyroiditis. Antibody testing showed positive thyroid antithyroglobulin antibodies and elevated thyroid-stimulating antibodies (TSI). A radioactive iodine uptake test was ordered, revealing increased contrast uptake. These findings suggested that the cause of thyroid dysfunction was Graves’ disease. The patient was started on Methimazole 20mg per day and discharged home after scheduling an outpatient follow-up appointment with the endocrinologist. This case is one of the rare cases of thyrotoxicosis attributable to Graves’ disease related to pembrolizumab therapy. To the best of our knowledge, two studies in the literature reported three cases of ICPi-induced thyrotoxicosis with thyroid antibody positivity following anti-PD-1 antibody therapy. Presentation: No date and time listed