Abstract: Objective  To investigate the clinical characteristics,  key points of diagnosis and therapeutics,  and other relevant risk factors of mycoplasma pneumoniacombined pulmonary thromboembolism in children. Methods  A retrospective study was conducted by analyzing a child patient with mycoplasma pneumoniacombined pulmonary thromboembolism,  together with literature review,  to investigate the clinical characteristics,  key points of diagnosis and therapeutics,  and other relevant risk factors of this rare incidence. Results  The child patient was a 7 year old girl at school age. Her major symptom included fever,  cough and discomfort in respiratory tract. Transient chest pain,  dyspnea and hypoxemia appeared in her initial stage of hospitalization. The left lower lung was percussed with voiced sound. The breathing voice from left chest was reduced,  while a little moist rale could be heard. Adjuvant examination: pleural effusion was light yellow and clear. Mycoplasma antibody IgM1∶320,  blood Ddimer 11.8 mg/L. CTA showed filling defect in partial branches of left upper pulmonary artery and right lower pulmonary artery. Echocardiography showed thrombosis at the beginning site of left pulmonary artery,  ANA (+),  positive in lupus anticoagulant,  decreased plasma protein S activity (59.5%). No gene mutation related to coagulation disease was detected. After admission,  pulmonary thromboembolism,  mycoplasma pneumonia and pleural effusion were diagnosed. Latamoxef disodium combined with azithromycin was administered to prevent infection. Dexamethasone was administered to inhibit inflammation. After anticoagulation therapy by calcium heparin and rivaroxaban,  the symptoms and characteristics of the child were improved. Pleural effusion disappeared,  and Ddimer gradually decreased to 0.1 mg/L. Conclusion   Child patient with mycoplasma pneumonia can be considered with the probability of obtaining pulmonary thromboembolism when diagnosed with chest pain,  dyspnea,  especially with significant elevation of Ddimer concentration. Pulmonary angiography can make a definite diagnosis. CTA should be performed in children with multiple risk factors or high risk of pulmonary embolism in the early stage. Formation of thrombosis may be associated with excessive inflammation and vascular endothelial damage caused by mycoplasma infection.

Key words: pulmonary embolism, pneumonia, , mycoplasma；thrombosis