D2.395 - Erdosteine-induced multifocal fied drug eruption: a case series of five patients

Fixed drug eruption (FDE) typically presents as localized recurrent lesions; however, multifocal involvement is uncommon. Erdosteine is a widely prescribed mucolytic agent generally considered safe. We report a case series of multifocal FDE induced by erdosteine, highlighting its distinctive clinical pattern and diagnostic approach.

Five patients with recurrent, multifocal, well-demarcated erythematous to violaceous patches following erdosteine exposure were retrospectively analyzed. Clinical characteristics, latency periods, lesion distribution, and diagnostic evaluations were reviewed, with particular attention to patch testing (20% erdosteine with petrolatum) and open label oral provocation tests.

All patients developed multifocal FDE after administration of common cold medication including erdosteine, with reproducible recurrence at identical sites upon re-exposure. Lesions mainly involved the trunk and extremities and resolved with residual hyperpigmentation. Symptom onset occurred within 1 hour to 3 days after drug intake. Patch tests with erdosteine were negative in all patients. One patient developed generalized eruptions with identical morphology 48 hours after patch testing, precluding oral provocation. In the remaining four patients, oral provocation tests were all positive.

This case series demonstrates that erdosteine, a commonly perceived safe mucolytic agent, can induce multifocal fixed drug eruption. While patch testing showed limited value, oral provocation testing enabled reliable diagnosis in most cases. Clinicians should consider erdosteine as a potential culprit in multifocal FDE to ensure timely diagnosis and prevention of recurrence.