Therapeutic Plasma Exchange as a Bridging Therapy for the Definitive Treatment of a Patient with Graves' Disease and Methimazole-Induced Liver Injury.

Introduction: Graves' disease (GD) is an autoimmune condition affecting the thyroid gland. The aim of treating GD is to control the symptoms of hyperthyroidism and achieve long-term remission. Antithyroid drugs (ATDs) are the medications of choice among newly-diagnosed GD patients as they are easy to be delivered and cause remission in more than 50% of patients. However, ATDs increase the risk of hepatotoxicity, especially among patients with liver abnormalities. Patients who cannot tolerate ATDs should receive definitive therapy such as radioactive iodine (RAI) or surgery. In order to minimize the risk of thyroid storm during these procedures, patients should be in euthyroid condition and receive bridging therapy. Therapeutic plasma exchange (TPE), which aims to remove thyroid hormones from plasma, is one of the modalities that can be considered as a bridging therapy during the perioperative period among GD patients who cannot tolerate ATD.

Case Presentation: A 35-year-old man with general weakness and thyrotoxicosis symptoms was admitted to the emergency room. Lid retraction, diffuse Goiter, and tremors were evident. Laboratory findings revealed TSH = 0.005 µIU/mL, FT4 = 7.77 ng/dL, TRAb = 9.90 IU/L, ALT = 123 U/L, total bilirubin = 23.94 µmol/L, and direct bilirubin = 10.26 µmol/L. Ultrasonographic examination showed the enlargement of the thyroid gland, and abdomen ultrasonographic evaluation showed mild hepatomegaly with mild fatty infiltration. The patient was diagnosed with GD, suspected thyroid storm, elevated liver transaminases, and fatty liver disease. The patient then received methimazole, propranolol, and glycyrrhizin. During observation, the patient developed drug-induced liver injury (DILI) evidenced by an increase in liver enzymes (ALT up to 1023 U/L) and the elevation of total bilirubin to 258.21 µmol/L, so methimazole was stopped. After discontinuing methimazole, liver injury improved. However, thyrotoxicosis symptoms returned, so the patient underwent a total thyroidectomy. In order to achieve a euthyroid status before surgery, five sessions of therapeutic plasma exchange were performed, which improved the signs and symptoms of hyperthyroidism and retained the thyroxine hormone within the normal range. Thyroidectomy was then performed successfully without serious complications (e.g., thyroid storm, etc.).

Conclusions: Therapeutic plasma exchange is a safe and effective bridging therapy for GD patients who require thyroidectomy but cannot tolerate ATDs.