Neutropenic enterocolitis with colon perforation during antithyroid therapy

Agranulocytosis, a rare but severe side effect of antithyroid drugs (ATDs), can lead to life-threatening complications such as neutropenic enterocolitis, an inflammatory condition of the colon with risks of bowel perforation and sepsis. A 43-year-old female with hyperthyroidism developed agranulocytosis after 25 days of methimazole therapy, presenting with fever and sore throat. Despite discontinuing methimazole and starting broad-spectrum antibiotics and G-CSF, her condition worsened, leading to confirmed colon perforation. Due to her poor condition, conservative management was maintained. After 13 days of G-CSF therapy, her neutrophil count and symptoms improved. She underwent a total thyroidectomy on day 42 and a hemicolectomy on day 73, and was later completely recovered and discharged. Methimazole-induced agranulocytosis with neutropenic enterocolitis is rare but critical. Early recognition, immediate discontinuation of ATDs, and conservative management, including G-CSF, are essential for improved outcomes.