Fixed Drug Eruption: Two Distinct Clinical Presentations

Abstract

Background: Fixed drug eruption (FDE) is a rare cutaneous adverse drug reaction of immuno-allergic origin, characterised by an eruption of erythematous lesions that leaves residual hyperpigmentation. The eruption recurs at exactly the same site upon re-exposure to the offending drug. This report describes two clinically distinct presentations associated with paracetamol and sulfamethoxazole/trimethoprim. Presentation of case: Case 1: A 41-year-old man presented with a mucocutaneous eruption 24 hours after taking paracetamol, with a history of two similar previous episodes in which identical lesions appeared at the same sites following ingestion of this medication. Case 2: A 40-year-old woman presented with pruritic erythematous lesions on the body that had been evolving for one day, occurring 30 minutes after taking sulfamethoxazole/trimethoprim for a urinary tract infection, with a history of a similar episode six months previously. Discussion: FDE is considered a type IV delayed-type hypersensitivity reaction, although its onset is relatively rapid. Clinical presentation varies and includes bullous, mucosal, and non-pigmenting forms. Skin biopsy is not strictly required for diagnosis, which remains primarily clinical. The main culprit drugs include analgesics, antiepileptics, and NSAIDs. The outcome is generally favourable, with lesion resolution leaving residual hyperpigmentation. Upon re-exposure to the culprit drug, lesions recur at the same sites and may also affect previously spared areas. Management relies on identifying and strictly avoiding the responsible agent. Conclusion: Fixed drug eruption is a characteristic cutaneous adverse reaction defined by well-circumscribed lesions, residual hyperpigmentation, and recurrence at the same sites during subsequent episodes. The diagnosis should be suspected on the basis of these clinical features.