Endocrine Abstracts

Background: Haematological side effects of Carbimazole such as aplastic anaemia, thrombocytopenia and agranulocytosis are widely reported. However, Carbimazole induced haemolytic anaemia is rare. Proplythiouracil is known to cause leucopenia, agranulocytosis, bone marrow hypoplasia and pancytopenia. Nevertheless, Propylthiouracil associated haemolytic anemia is rarely reported. In such situations, the options for managing Hyperthyroidism are limited, especially in frail elderly individuals. We report a case of Carbimazole and Propylthiouracil induced haemolytic anaemia which resolved following discontinuation of the medication and starting on steroids.

Case presentation: An 83-year-old female presented with tiredness, low mood, indigestion, palpitations and anxiety. She was mildy thyrotoxic with no clinically evident goitre. TSH was suppressed at <0.02 mU/l with a fT4 of 32.1 pmol/l. Her thyroid receptor antibody (TRAb) was negative. Thyroid uptake scan revealed a total uptake of 0.7% with 0.5% left lobe and 0.3% right lobe. Both thyroid lobes appeared large with heterogeneous uptake, but there were no discrete avid nodules. The diagnosis of hyperthyroidism due to thyroid autonomy was made and she was started on Carbimazole 10 mg once daily. After 3 weeks, she presented with jaundice and worsening tiredness. On clinical evaluation she was anaemic with a haemogloblin of 1 g/l. The reticulocyte count of 412×109/l, with polychromasia, spherocytes and positive auto anti-e, pan reactive IAT antibody confirmed the diagnosis of Carbimazole induced haemolytic anaemia. Carbimazole was discontinued and high dose corticosteroid was started which was gradually tapered according to the clinical response. Six months following discontinuing Carbimazole, she presented with a relapse of hyperthyroidism. Her TSH was suppressed (<0.1 mU/l) with raised Free T4 32.1 pmol/l and Free T3 7.1 pmol/l. Due to the frailty, the alternative treatment options were limited. Therefore, she was started on a trial of propylthiouracil 1 mg twice daily with close monitoring. Subsequently, she developed a recurrence of haemolytic anaemia with a haemoglobin of 80 g/l just 1 week following Propylthiouracil initiation. Propylthiouracil was discontinued and she was treated with corticosteroids. Cholestyramine 1 g once daily was started as an adjunctive treatment for hyperthyroidism. She responded well to the medications with improvement in the haemoglobin and remains euthyroid to date.

Conclusions: Antithyroid induced haemolytica anemia is an extremely rare adverse effect of the medication. A patient developing haemolytic anaemia to both Carbimazole and Propylthiouracil has not been documented in the literature. The awareness of rare adverse effects related to antithyroid medication and timely management can improve the patient outcomes.