12616 Pembrolizumab-induced Autoimmune Adrenal Insufficiency: A Case Report And Literature Review

Abstract Disclosure: A. Calderon: None. E. Calderon-Martinez: None. J. Shakil, MD: None. A. Kansara: None. Immunechekpoint inhibitors (ICI)-related Primary Adrenal Insufficiency (PAI) is an uncommon entity. Compared to other endocrine-related adverse effects (irAES), antibody detection is less consistent. TPO and GAD65 antibodies are usually present in about 40-80% of the cases with hypothyroidism, hyperthyroidism, and diabetes. On the contrary, case reports and series for PAI seldom report the presence or absence of 21OH antibodies. We present a case and perform a literature review of PAI, in a patient who received pembrolizumab and developed PAI with 21 hydroxylase antibodies. A 62-year-old man with history HIV on ART (last CD4 count 590 cells/mm3) and locally advanced urothelial cancer on Pembrolizumab, presented with nausea, vomiting, abdominal pain, and decreased urine output. He was noted to be confused, and in hypoactive delirium. On admission, his chemistry panel he was noticed to have normal sodium and potassium levels. The CT scan of the abdomen revealed regional enteritis and was started on IV fluid therapy. His adrenal glands were described as normal on imaging. On the 16th day of hospitalization, the patient became unresponsive and hypotensive. He was transferred to the ICU. His sodium level was 132 mEq/L and potassium level was 6.1 mEq/L, bicarbonate level was 18 mEq/L, calcium of 10.3 mg/dl, and eosinophils of 15%. Random cortisol levels measured before administration of steroids were undetectable twice, 9 hours apart, with an ACTH level of 94. He underwent an ACTH stimulation test with cosyntropin 250 mcg IV with resulting undetectable cortisol levels after 30 and 60 minutes. CT and MRI of the brain showed no signs of hypophysitis. He was started on high-dose hydrocortisone with improvements in his mental status, hypotension, and gastrointestinal symptoms. He was discharged on hydrocortisone. His 21-Hydroxylase antibody was later found out to be positive. After combination immunotherapy regimens, CTLA-4 inhibitors are the most common to cause any irAE, however endocrine irAE particularly are mostly associated with PD-1 inhibitors. Among these, thyroid and pituitary disorders are the most common ones. Reports show that about 10% of patients receiving immunotherapy will develop endocrinopathy. ICI-induced PAI has been reported to occur in 7.6% of patients receiving combination therapy, and 2% of patients receiving Pembrolizumab. It has been reported that only 15% of patients will recover adrenal function. A meta-analysis that gathered 15 cases of ICI-induced PAI, found that only 2 cases had positive 21-hydroxylase antibodies. In our presented case, we have robust biochemical confirmation of PAI, with positive 21 hydroxylase antibody, after being on pembrolizumab for 9 months. Further information is needed to establish the pathophysiology, presentation, and prognosis of ICI-related PAI when anti adrenal antibodies are positive. Presentation: 6/1/2024