A case report of severe Mycoplasma pneumoniae pneumonia complicated by plastic bronchitis and Kawasaki disease.

backgroundWe report the first documented case of macrolide-resistant Mycoplasma pneumoniae (MRMP) infection simultaneously complicated by both plastic bronchitis (PB) and Kawasaki disease (KD), expanding our understanding of severe MRMP-associated immune dysregulation. CASE PRESENTATION: A 7-year-old male presented with persistent high fever (39.8 °C), paroxysmal cough, and mucocutaneous manifestations. Diagnosis was established through multiple modalities: chest CT revealed bilateral consolidation with segmental airway narrowing; bronchoscopy demonstrated characteristic bronchial casts with focal mucosal necrosis; echocardiography showed right coronary artery dilation (Z-score + 2.334); and targeted next-generation sequencing (tNGS) identified MRMP with the A2063G mutation, alongside Streptococcus pneumoniae and Staphylococcus aureus co-infections. Treatment included oral doxycycline after macrolide failure, high-dose IVIG (2 g/kg), methylprednisolone (3 mg/kg/day), and therapeutic bronchoscopy. Complete resolution of coronary dilation and respiratory symptoms was achieved by the one-month follow-up.

conclusionsThis unprecedented case demonstrates how MRMP infection can trigger simultaneous, severe immune-mediated complications through shared inflammatory pathways. In regions with high MRMP prevalence (> 90%), clinicians should maintain vigilance for atypical manifestations in refractory pneumonia. Early bronchoscopy and tNGS for comprehensive pathogen identification are essential, while combined therapy with appropriate alternative antibiotics, corticosteroids, and IVIG can effectively manage these complex cases. CLINICAL TRIAL NUMBER: Not applicable.