Mycoplasma pneumoniae–associated reactive infectious mucocutaneous eruption (RIME) confirmed by multiplex PCR: a case-based review

Abstract Reactive infectious mucocutaneous eruption (RIME) is a para-infectious syndrome characterised by prominent mucositis with limited cutaneous involvement, typically following a respiratory illness. Diagnostic uncertainty is common because RIME may mimic erythema multiforme and drug-induced Stevens–Johnson syndrome/toxic epidermal necrolysis (SJS/TEN), particularly when antibiotics have been initiated shortly before onset. We report a 25-year-old woman presenting with fever, generalised maculopapular rash, severe oral erosions with odynophagia, genital involvement, eyelid and lip oedema, and haemorrhagic lip erosions. Chest radiography demonstrated a right lower lobe opacity consistent with pneumonia despite minimal respiratory symptoms. The eruption developed five days after initiation of oral cefuroxime for a presumed respiratory tract infection. There was no epidermal detachment and the Nikolsky sign was negative; ophthalmologic assessment showed no ocular involvement. Mycoplasma pneumoniae infection was confirmed by sputum multiplex PCR and supported by serology. The clinical phenotype and microbiologic confirmation supported RIME rather than drug-induced SJS/TEN. The patient improved with intravenous corticosteroids, azithromycin, and supportive care, with complete resolution at one-month follow-up. This case-based review summarises diagnostic clues, highlights the role of multiplex PCR in aetiologic attribution, and outlines pragmatic management principles to reduce morbidity and avoid misclassification as a severe drug reaction.