Immunotherapy Induced Adrenal Insufficiency: An Underdiagnosed Cause of Persistent Hypotension in Cancer.

Endocrinopathies following immunotherapy have infrequently been documented in the literature. Adrenal insufficiency is a rare consequence of pembrolizumab immunotherapy, with incidence reported to be between 0.98 and 1.3%. We present the case of a 34-year-old female with triple negative breast cancer on chemotherapy who presented with generalized weakness with tachycardia, tachypnea and hypotension unresponsive to fluids. Despite initial improvement with intravenous hydrocortisone and midodrine, the patient continued to be symptomatically hypotensive following discharge and required re-admission. AM cortisol level was found to be < 0.5 ug/dl and ACTH was <1.5 pg/dL, consistent with secondary adrenal insufficiency. CT abdomen and pelvis was unremarkable for adrenal pathology. Patient had been initiated on pembrolizumab (Keytruda) 4 months prior to presentation as part of neoadjuvant chemotherapy. The patient was provided supportive treatment with discharge on fludrocortisone, prednisone, and midodrine. This case reports an unusual consequence of immune checkpoint inhibitors, in which early diagnostic testing, identification, and management is critical.