LBODP011 Pembrolizumab Induced Hypophysitis And Resultant Isolated ACTH Deficiency Presenting As Secondary Adrenal Insufficiency.

INTRODUCTION: Pembrolizumab is a novel human immunotherapeutic monoclonal antibody directed against PD-1 (programmed death receptor 1). It has been approved by the FDA for treatment of many malignancies including breast cancer. Although it has improved survival for many oncological conditions, it has been linked to a variety of endocrinopathies. We present a case of Pembrolizumab induced hypophysitis with isolated ACTH deficiency presenting as secondary adrenal insufficiency. CASE PRESENTATION: A 36 year old female with a history of breast cancer treated with chemotherapy and surgery, presented with intractable nausea and vomiting. She reported not being able to keep anything down for 4-5 days and had experienced multiple episodes of non-bilious, non-bloody emesis. She endorsed dizziness, but denied fever, chills, shortness of breath, abdominal pain, or problems with urination/bowel movements. She had been treated with Pembrolizumab with the last dose being 4 months prior to presentation. On arrival, vitals included temperature 98.4 F, BP 104/62 mm Hg, Heart rate 104 bpm, RR 16 with SpO2 100%. Labs were significant for WBC count 3.65 K/uL (3.81 - 8.94), Eosinophils 10.4% (0.1 - 6; she was noted to have eosinophilia prior to presentation), Hemoglobin 11.6 g/dL (11 - 14.9), Sodium 140 mmol/L (136-145), Potassium 3.4 mmol/L (3.4 - 5.1), Glucose 57 mg/dL (70 - 100), Lactate 0.7 mmol/L (0.2 -2), Lipase 23 U/L (13 - 60), Urine HCG negative, Urinalysis negative for nitrites and leukocyte esterase, TSH 1.22 uIU. ml (0.5 -5.7) and AM cortisol 0.4 ug/dL (6 - 18.4). Endocrinology was consulted and further work up was sought: ACTH <5 pg/ml (7.2 - 63) and Cortisol 30 - 60 minutes after cosyntropin stimulation 3.6 ug/dL. Prolactin, free T4, FSH and LH were within normal limits. MRI brain showed a prominent pituitary gland with enhancement and interval loss of posterior pituitary bright spot representing lymphocytic hypophysitis. She was started on Solu-Cortef and her symptoms resolved. She was discharged on hydrocortisone with education on sick day rules for secondary adrenal insufficiency. DISCUSSION: Adrenal insufficiency secondary to immunotherapy is a rare, emergent and dangerous condition. The key to successful management is early recognition. In patients treated with immunotherapy agents, non-specific symptoms such as nausea, vomiting, fatigue (which are common adverse effects of chemotherapy) should prompt urgent evaluation with hormonal workup. Evidence suggests that eosinophilia may be an early indicator before the onset of symptoms which was evident in our case. Radio-graphic imaging is helpful for diagnosis. Treatment entails high dose corticosteroids for acute crisis followed by physiological maintenance dosing. Patients should be educated on sick day rules for adrenal insufficiency. Presentation: No date and time listed