Antithyroid drugs have been used for more than 50 years for the management of hyperthyroidism. Most patients tolerate treatment well, but some may develop rare life threatening side effects such as agranulocytosis and aplastic anaemia. Clinical experience with the latter condition is extremely limited. We report on a case of carbimazole-induced aplastic anaemia caused by hypocellular bone marrow and associated plasmacytosis in a thyrotoxic patient chronically treated with carbimazole. This resolved after substitution with propylthiouracil. The clinical course was complicated by neutropaenic septicaemia and atrial fibrillation.
Study site: University Malaya Medical Centre (UMMC), Kuala Lumpur, Malaysia