7650 Thionamide Induced Pancreatitis and Agranulocytosis, a Rare Case of Concurrence

Abstract Disclosure: J. Lin: None. J. Shariff: None. Introduction: Thionamides are considered first line in the treatment of Graves’ Disease due to their efficacy and safety. We present a case of Graves’ in which methimazole resulted in not only agranulocytosis but also pancreatitis. Case Report: A 29yo female was diagnosed with Graves’ 5 months postpartum by her PCP. Her labs at diagnosis revealed a TSH 0.01 uIU/mL, free T4 of 6.4 ng/dL, and positive TRAb. She was started on methimazole 10mg and propranolol 20mg three times a day by her PCP. One month after starting treatment, she presented to the ED due to throat pain/fevers and was diagnosed with tonsilitis. She was given a 10mg dose of dexamethasone and sent home with antibiotics. No labs were drawn that visit. She went to her PCP 3 days later due to persistent symptoms and nausea/vomiting. A CBC revealed she had a WBC of 0.7 K/uL and an absolute neutrophil count (ANC) of 0.1 K/uL. Her last dose of methimazole had been the day prior to seeing her PCP. It was recommended she be seen in the ED due to concern for agranulocytosis where she was started on antibiotics and a CT abdomen pelvis with contrast revealed she had acute pancreatitis. She was admitted and started on filgrastim 5mcg/kg daily for thionamide-induced agranulocytosis. Her pancreatitis improved with conservative measures. Her propranolol was resumed at 30mg three times a day with symptom improvement. On her fifth hospitalization day, her ANC had recovered to 2.22 K/uL, WBC was 6 K/uL. Her free T4 was 1.65 ng/dL, free T3 4.1 pg/mL, TSI 40 IU/L. This change was suspected to be from propranolol, steroids, iodine load from her CT, and prior methimazole use. It was strongly recommended she pursue surgery that hospitalization given inability to treat her Graves’ medically. The patient refused, stating she wished to consider her options further outpatient. She would be seen one week later in a satellite ED. Her free T4 was 5.9 uIU/mL, T3 30 pg/mL, TSH 0.010 uIU/mL. She left against medical advice. She subsequently declined further endocrine follow-up. Clinical Lessons: Thionamide-induced agranulocytosis is a rare but known complication of use, with some studies showing a prevalence as low as 0.2-0.5% 1. Pancreatitis is a lesser-known complication of thionamides. There are several case reports of its occurrence, with the European Medicines Agency even listing it in the potential adverse reaction. Absolute risk of occurrence remains low, some studies showing 0.4% 1. This case shows a rare concurrence of two uncommon complications from thionamide use and brings awareness to both pancreatitis and agranulocytosis as potential adverse events. References: 1: Lee SY, Pearce EN. Hyperthyroidism: A Review. JAMA. 2023 Oct 17;330(15): 1472-1483. doi: 10.1001/jama.2023.19052. PMID: 37847271. Presentation: 6/2/2024