Carbimazole-induced acute myeloid leukemia: A very rare case report and review of the literature.

Neutropenia is a common side effect in hyperthyroid patients with long-term use of antithyroid drugs. Antithyroid drugs have been used for the management of hyperthyroidism and rarely may cause life-threatening side effects such as pancytopenia and very rarely may cause acute leukemia. The current case report is of a 34-year-old man diagnosed with hyperthyroidism who presented with pancytopenia after treatment with carbimazole for past 7 months; he initially improved with supportive treatment. The patient restarted treatment with carbimazole but with a reduced dose. He was readmitted for fever and high total leukocyte counts after 3 months of restarting carbimazole. The patient was thoroughly investigated, and bone marrow aspiration examination showed acute myeloid leukemia. This presentation of acute myeloid leukemia was likely attributed to the reexposure to carbimazole, although the association of acute myeloid leukemia with autoimmune thyroid disease cannot be denied.