THU539 Pembrolizumab-induced Hypophysitis Occurring Concurrently With Takotsubo Cardiomyopathy

Disclosure: I. Nadeem: None. H.S. Chaudhry: None. S. Aslam: None. M. Asif: None. W.J. Khan: None. Abstract: Immune checkpoint inhibitors (ICI) are novel medications used to treat a wide range of solid organ tumors and work by stimulating the cellular immune response. With their increasing use, more and more multiorgan side effects including endocrine system are reported in the literature. Prompt recognition of these findings is vital for the safe clinical use of these agents. We report a case of a pembrolizumab-induced triad of hypophysitis, takotsubo cardiomyopathy, and pneumonitis. Case Report: A 72-year-old female with metastatic NSCLC on single therapy with pembrolizumab had received her second session three weeks before the presentation. She presented with progressive dyspnea and generalized weakness but no reported chest pain, fever, or chills. At presentation, she had a BP of 82/62 mmHg, and a pulse rate of 160/min; EKG showed new-onset atrial fibrillation with a rapid ventricular response (RVR) but no acute ischemic changes. Physical examination revealed a pale lady in distress due to shortness of breath. Laboratory analysis revealed hypophysitis with ACTH <5 pg/ml (7.2-63 pg/ml), aldosterone <4 ng/dl (<21ng/dl), TSH 0.26 uIU/ml (0.34-4.94 Uiu/ml), FSH 8.4 mIU/ml (low for age), LH 1.6 mIU/ml (low for age). She was managed with methyl prednisone 60 mg twice daily for seven days, followed by a taper to a final maintenance dose of 5 mg prednisone due to adrenal insufficiency. Unfortunately, two months post-discharge, she passed away at her home due to sudden cardiac death. Discussion: ICI is increasingly used for different malignancies and is frequently linked to various immune-mediated entities simultaneously or at separate times including the pituitary gland. The adverse effects involving the endocrine system are hypo- or hyperthyroidism, hypophysitis, adrenal insufficiency, and type 1 diabetes mellitus. Immune-mediated Takotsubo cardiomyopathy pneumonitis and hypophysitis are treated with systemic steroids with a slow taper and close monitoring of side effects from corticosteroids. Other options include pulse steroids, mycophenolate mofetil, and plasmapheresis on a case-by-case basis. The median onset of hypophysitis and pneumonitis was noted to be 76 and 90 days from the initiation of ICIs, respectively. The mortality rate is relatively high with these complications. Our case report underscores the importance of provider awareness for closely monitoring all patients treated with ICI for various multisystem complications. We anticipate that identifying and reporting these rare complications will help get data for developing monitoring protocols in the future and help other providers recognize these complications in their patients currently on ICI treatment and take appropriate management steps for patient safety. Presentation: Thursday, June 15, 2023