Unusual Manifestation of Post-Infectious Erythema Multiforme

Erythema multiforme presents as an acute skin rash characterized by symmetrical, round-shaped erythematous papules. It is typically triggered by herpes infections, Mycoplasma pneumoniae, or certain medications. In this case report, we describe a 12-year-old boy with no significant medical history who was admitted with gingivostomatitis and a generalized rash persisting for 5 days, accompanied by an unnoticed fever and declining overall health. Upon examination, the patient exhibited a fever of 39.2°C, gingivostomatitis characterized by erythematous plaques covered with vesicles across the lips, oral thrush, a maculopapular skin rash resembling erythema multiforme in a cockade pattern, and crusty lesions on an erythematous background in the genital area (penis and glans). The diagnosis confirmed erythema multiforme and gingivostomatitis caused by Chlamydia pneumoniae through respiratory PCR test and serological testing, which revealed elevated levels of IgM antibodies. Treatment with Clarithromycin resulted in significant clinical improvement, with lesion regression and achievement of a fever-free state within 72 hours. This case highlights the potential for atypical manifestations of Chlamydia pneumoniae infection in children.