目的 探讨儿童肺炎支原体肺炎（MPP）合并感染性心内膜炎（IE）这一罕见并发症的临床特点、诊断、治疗及预后，以提高临床医生对该疾病的认识和早期诊断。方法 回顾性分析2023年1月至2024年11月本院收治的5例MPP合并IE患儿的临床资料，包括临床表现、实验室检查、影像学结果、病原学检测、治疗及随访情况。结果 5例患儿发病年龄9（5~9.5）岁，男女比例3∶2，所有患儿均有发热、咳嗽表现，仅1例合并剑突下疼痛；发热持续时间12（9.5~15）天，发现赘生物时间为病程第10（8~12）天；所有患儿均经超声心动图诊断，D二聚体5.09(4.35~7.90)μg/mL 及FDP 10.56(7.20~24.71) mg/L明显增高，IL-6 55.45(33.02~95.56 ) pg/mL及乳酸脱氢酶746(568.45~838.9) U/L水平亦有增高。所有患儿呼吸道标本MP核酸检测阳性，但仅1例血流宏基因检测检出MP。所有患儿均接受手术切除赘生物，术后病理均证实为IE。经手术治疗后所有患者均给予抗感染及抗凝治疗，3例合并肺栓塞患者出院后继续给予抗凝治疗1~6个月。出院后复查彩色多普勒超声心动图均未见赘生物复发，无气促、胸痛、喘息等症状。结论 MPP所致感染性心内膜炎早期症状隐匿，缺乏特异性临床表现。MPP患儿若伴高凝状态，建议行彩色多普勒超声心动图筛查以便早期发现IE赘生物，避免漏诊，及时治疗预后良好。

Objective To investigate the clinical features, diagnosis, treatment, and prognosis of the rare complication of infectious endocarditis (IE) in children with Mycoplasma pneumoniae pneumonia (MPP), aiming to enhance clinicians' understanding and facilitate early diagnosis of this condition. Methods A retrospective analysis was conducted on the clinical data of 5 children with MPP complicated by IE admitted to our hospital from January 2023 to November 2024. The analysis included clinical manifestations, laboratory tests, imaging findings, etiological test results, treatment, and follow-up information. Results The median age of onset was 9 years (5-9.5) years, with a male-to-female ratio of 3:2. All patients presented with fever and cough; only one exhibited concomitant subxiphoid pain. Median duration of fever was 12 (9.5-15) days, and vegetations were detected on echocardiography at a median of 10 (8-12) days after disease onset. Elevated D-dimer levels 5.09 (4.35-7.9) μg/mL and fibrin degradation products 10.56 (7.2-24.71) mg/L indicated marked hypercoagulability, while increased IL-6 55.45 (33.02-95.56) pg/mL and lactate dehydrogenase 746 (568.45-838.9) U/L suggested significant systemic inflammation and tissue injury. All children tested positive for MP nucleic acid in respiratory specimens; however, only one had MP DNA detected in blood via metagenomic next-generation sequencing (mNGS). All underwent surgical excision of vegetations, with histopathological examination confirming the diagnosis of IE. Postoperatively, all received antimicrobial therapy and anticoagulation. Among them, three patients with confirmed pulmonary embolism continued long-term anticoagulation for 1-6 months post-discharge. Follow-up echocardiography revealed no vegetation recurrence, and no patient reported symptoms such as dyspnea, chest pain, or wheezing during the monitoring period. Conclusion MPP-related IE presents with nonspecific and often insidious early manifestations, posing challenges for timely diagnosis. In pediatric patients with MPP and evidence of hypercoagulability, routine echocardiographic screening is strongly recommended to enable early detection of IE and prevent diagnostic delays. With prompt diagnosis and comprehensive management, the prognosis is favorable.