Introduction: Carbimazole is a first line antithyroid drug for thyrotoxicosis management in UK. Its main but rare complications include allergic reaction and risk of neutropenia. Here we discuss the lesser reported situation in which a thyrotoxic patient who is in a remission from Aplastic anaemia was treated with Carbimazole.
Case Report: Out patient was seen in Ambulatory care with symptoms of heart failure along with tachycardia. Thyroid blood test showed severe thyrotoxicosis. After discussion with Haematologist and ENT surgeons, patient was consented to have low dose Carbimazole with monitoring for any clinical or biochemical relapse of Aplastic anaemia. She became euthyroid both clinically and biochemically within 6 months of starting carbimazole without any relapse of her aplastic anaemia and was referred to surgeons for definitive treatment.
Discussion: The cases of carbimazole induced neutropenia are well known in literature. Likely mechanism involves bone marrow suppression along with the effect on GCSF. There is a limited data available regarding use of carbimazole in a thyrotoxic patient who has a past medical history of treated Aplastic anaemia.
Conclusion: Although the option of admitting patient and to use Lugols iodine before surgery could be used but there was a high risk of thyroid storm. Therefore, treated with low dose carbimazole with bloods monitoring twice per week for any signs of Aplastic anaemia relapse. This case shows that carbomazole in low dose can be used with caution and for a limited time in thyrotoxic patient with history of Aplastic anaemia as a bridge to definitive treatment in the form of surgery.