A Rare Complication after Post-Pandemic Re-Emergence of M. pneumoniae

Abstract

Background: After the COVID-19 pandemic, Mycoplasma pneumoniae, a common respiratory pathogen, has resurged globally, with increased cases of rare complications like reactive infectious mucocutaneous eruption (RIME). RIME is characterized by a mucositis involving ≥2 surfaces and limited skin lesions following a respiratory infection. Here we present first two cases of RIME diagnosed in our hospital in children. Case Presentation Summary: Two previously healthy boys, aged 13 (Patient A) and 17 (Patient B) were hospitalized in 2024 due to a history of fever and mucosal lesions. Physical examination of both patients revealed signs of respiratory infection, including cough, cervical lymphadenopathy, crackles on auscultation, and oral mucosal eruptions with ulcers leading to serosanguinous slough and hemorrhagic crusts on the lips. While Patient A also had purulent bilateral conjunctivitis, few vesicular lesions on his right palm and left foot and elevated inflammatory markers (CRP 72.5 mg/L; PCT 1.3 μg/L), Patient B presented with widespread targetoid lesions, balanoposthitis, and left lung consolidation with low CRP. Patient B was immediately treated with clarithromycin due to high M. pneumoniae prevalence and atypical pneumonia, whereas Patient A was initially suspected to have severe stomatitis and first treated with penicillins, metronidazole, and acyclovir, which resulted in worsening of the condition: spreading oral erosions and facial swelling. Three days later M. pneumoniae IgM antibodies tested positive, leading to a diagnosis of RIME and subsequent treatment with clarithromycin. The diagnosis of Patient B was serologically confirmed on the 2nd day of hospitalization. Both patients showed significant improvement within 48 hours of treatment. Learning Points/Discussion: Cases of RIME, previously known as Mycoplasma induced rash and mucositis, have increased after COVID-19 pandemic due to a resurge of M. pneumoniae prevalence. RIME may be mistaken for other infections like herpes, coxsackievirus infection or Steven-Johnson syndrome, leading to diagnostic delays.