Erythema Multiforme Triggered by Bacterial Infection: A Case Report

Introduction Erythema multiforme (EM) is an acute immune-mediated condition characterized by distinctive “target” lesions on the skin and involvement of mucosal membranes. The condition can be triggered by infections or medications[1], and it is often associated with mucosal erosions or blisters involving the oral, ocular, and genital mucosa [2]. The disease may present with atypical manifestations, including a more severe form, known as erythema multiforme major, which involves more extensive mucosal involvement and can be complicated by secondary infections [3]. In this report, we describe a case of EM that was triggered by a bacterial infection. Case Presentation A 30-year-old male with no significant history was diagnosed with bacterial pneumonia and started on cefuroxime. He later developed an upper lip blister, spreading to the oral cavity and conjunctiva with redness and swelling. Recurrent fever, a confluent maculopapular rash, and mucosal erosions in the oral and genital areas followed. A mouth swab culture for aerobes and fungi was negative. Erythema multiforme (EM) was diagnosed. Cefuroxime, acyclovir, and glucocorticoids were initiated. Herpes simplex virus infection was investigated, but cultures were negative. The patient showed significant improvement in symptoms and inflammatory markers. Discussion In this case, erythema multiforme was likely triggered by a bacterial infection, but other differential diagnoses were considered, including severe forms of cutaneous reactions like Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). The involvement of the mucosal membranes, presence of fever, and the characteristic rash were key clinical features that guided the diagnosis. Given the complexity of the presentation, careful monitoring and differential diagnosis were essential. The patient's response to treatment supports the diagnosis of EM triggered by bacterial pneumonia. Conclusions One of the most important aspects in clinical practice is never losing vigilance and suspicion during treatment. Although the primary cause of erythema multiforme was identified as a bacterial infection, the possibility of other triggers, including medication-induced reactions, must always be considered, especially if the patient does not improve as expected.