SAT-454 Visual Hallucination, an Unusual Presentation in Immunotherapy Induced Adrenal Insufficiency - A Case Study

Abstract Disclosure: U.B. Zakia: None. M. Aiad: None. G. Smith: None. M. Wilson: None. Background: Adrenal insufficiency (AI) is a significant endocrine toxicity caused by immunotherapy (3,4). Immune checkpoint inhibitors may result in primary (n=11), secondary (n=191), or mixed types (n=4) of adrenal insufficiency. Clinical Case: Our patient, a 60-year-old Caucasian male with a history of smoking (9 pack years), anxiety, depression, and right lower lobe adenocarcinoma of the lung, underwent resection for the primary tumor but experienced recurrence in the lymph nodes and right pleural effusion. He received 5 cycles of chemotherapy, including carboplatin, pemetrexed, and pembrolizumab over three months. Upon admission, he presented with nausea, vomiting, weakness, significant weight loss, diarrhea, and orthostatic dizziness. He was afebrile with stable vital signs, but lab results showed hyponatremia (sodium 133 mmol/L) and low bicarbonate (16 mmol/L). CT scans indicated possible cystitis and moderate pleural effusion, with a normal head CT. The following day, the patient began experiencing visual hallucinations, including seeing lions on the TV screen. His cortisol levels were low (1.2 and 1.6 ug/dL), and ACTH was also low (3.3 pg/mL), confirming secondary adrenal insufficiency induced by pembrolizumab. Hydrocortisone was started, and endocrinology was consulted for management. The patient improved and was discharged on oral hydrocortisone with follow-up appointments. At his oncology follow-up, pembrolizumab was discontinued, and his symptoms continued to improve with steroid therapy. The patient’s non-small cell lung cancer tested positive for PD-L1, which enhances pembrolizumab efficacy. Approximately 21% of immunotherapy patients develop endocrinopathies, often due to immune-related hypophysitis, causing low ACTH and secondary adrenal insufficiency. Symptoms include weakness, nausea, vomiting, anorexia, hypotension, and psychosis. Theories suggest that hyponatremia may cause cerebral edema and confusion, or low glucocorticoids could impair memory and executive function, contributing to psychosis. Additionally, reduced glucocorticoids may increase endorphin levels, leading to hallucinations. Psychosis typically improves with hydrocortisone, but steroids can also cause psychiatric symptoms. In this case, visual hallucinations occurred before steroid treatment. After ruling out alcohol withdrawal, anesthesia effects, and delirium, steroid therapy successfully resolved the patient’s symptoms. Timely diagnosis and treatment of adrenal insufficiency are critical for managing this potentially life-threatening condition. Conclusion: In patients undergoing Pembrolizumab treatment, endocrine toxicities should be regularly assessed through laboratory tests with high clinical suspicion. Presentation: Saturday, July 12, 2025