Introduction: Agranulocytosis induced by synthetic antithyroid drugs is a rare but serious complication of hyperthyroidism treatment, usually presenting with symptoms of a common infection. Severe cutaneous manifestations are exceptional. Case report: We report the case of a 58-year-old female patient treated with high-dose methimazole for hyperthyroidism, admitted with extensive bullous dermohypodermitis of the upper limb and ipsilateral chest wall, associated with a deterioration in her general condition. Laboratory investigations revealed severe agranulocytosis complicated by a major inflammatory syndrome. Imaging ruled out necrotising fasciitis. Immediate discontinuation of synthetic antithyroid drugs, initiation of empirical antibiotic therapy and multidisciplinary management led to a favourable clinical and laboratory outcome. Discussion: This observation highlights an unusual and misleading presentation of agranulocytosis induced by synthetic antithyroid drugs, which can constitute a genuine diagnostic pitfall. The prescription of high initial doses, the absence of prior laboratory investigations, and the concomitant use of corticosteroids likely contributed to the severity of the clinical picture. This case underscores the importance of heightened vigilance in the face of any severe infection in a patient being treated with antithyroid drugs. Conclusion: Bullous dermohypodermitis may, in exceptional cases, reveal agranulocytosis induced by antithyroid drugs. Prescribing in accordance with guidelines, appropriate monitoring and clear patient information are essential to prevent this serious complication.
Niyogushima et al. (Thu,) studied this question.