Endocrine Abstracts

Case History: A 23-year-old Bengali woman with a 2-year history of Graves’ disease presented to the endocrine day unit with a widespread, pruritic, vasculitic-looking rash. She was treated with Carbimazole since diagnosis but was poorly compliant. One month prior to presentation, her Carbimazole dose was increased from 20 mg daily to 60 mg daily, as she remained biochemically thyrotoxic (Free T4 79.9 pmol/l, T3 34.8 pmol/l and TSH < 0.01 mU/l). The rash started on her lower legs and spread to the abdomen and arms. She felt systemically well and there was no mucosal or ophthalmic involvement. She had no personal or family history of dermatological issues, no previous drug reactions and no recent travel history. On examination, there was a purpuric, confluent, papular rash affecting her limbs and trunk, with scanty bullous lesions over both lower legs. Carbimazole was stopped with some immediate improvement in symptoms and urgent dermatological review was arranged.

Investigations: Full blood count demonstrated a marked eosinophilia of 1.4 + 10⁹/l (0–0.5) with a total white cell count of 7.8 + 10⁹/l (4–11). C-reactive protein was 2 mg/l (0–5). Alkaline phosphatase was chronically raised at 257 units/l (30–130). Bilirubin was normal at 6 mmol/l (0–21). Autoimmune serology, complement C3d, anti-streptolysin o titre and immunoglobulins were normal.

Results and Treatment: Punch biopsies taken from arm and leg lesions revealed spongiotic eosinophilic dermatitis with no evidence of vasculitis or leucocytosis. Subsequent fungal stains and direct immunofluorescence testing for immunoglobulins and complement C3 were negative. She was treated with oral Prednisolone, topical Clobetasol propionate and emollients for 4 weeks, with complete resolution of skin lesions and eosinophilia. She became hyperthyroid after cessation of Carbimazole and underwent successful definitive treatment with radioiodine.

Conclusions and points for discussion: • Rashes are a well-recognised side effect of Carbimazole. Although most are mild and self-limiting, severe reactions including ANCA-associated vasculitis can occur.

• Severe eosinophilic reactions to antithyroid drugs are rare and idiosyncratic. Delayed reactions and systemic involvement (DRESS syndrome, eosinophilic pleural effusion) have been reported.

• Important to consider systemic effects and associated symptoms in patients presenting with dermatological reactions to antithyroid medication.

• Definitive treatment for Graves’ disease should be considered in cases of drug reaction.

• Prompt dermatological referral and histological examination are imperative in cases of antithyroid drug-induced rash. If dangerous differential diagnoses can be excluded, treatment continuation may be possible.