[Clinical characteristics and therapeutic experience with rivaroxaban in children with <i>Mycoplasma pneumoniae</i> pneumonia associated with pulmonary thromboembolism].

<b>Objective:</b> To evaluate the efficacy and safety of rivaroxaban and investigate the clinical features of <i>Mycoplasma pneumoniae</i> pneumonia (MPP) associated with pulmonary thromboembolism (PTE) in children. <b>Methods:</b> A case series study was conducted on 36 children, diagnosed with MPP associated with PTE and hospitalized in our institution from January 2020 to June 2024 of Department of Pediatric Respiratory, Shandong Provincial Hospital Affiliated to Shandong First Medical University. Clinical data and follow-up information were collected to analyze their clinical characteristics, outcomes, and adverse events to rivaroxaban. Comparison of coagulation indices before and after treatment with rivaroxaban using the Mann-Whitney rank sum test. <b>Results:</b> Among the 36 children, there were 27 males and 9 females, and the age of onset was (7.8±2.8) years. PTE was diagnosed (17±6) days after the onset of MPP. Thirty-four cases (94%) were classified as low-risk PTE, and 13 cases (36%) had thromboembolism of multiple anatomic sites. All patients presented with cough and fever, manifesting as shortness of breath in 33 cases (92%), chest pain in 12 case (33%), hemoptysis in 6 case (17%) and dyspnea in 5 cases (14%). All Pulmonary artery involvement was demonstrated by CT pulmonary angiography in all 36 children. The D-dimer level was 5.1 (4.2, 12.2) mg/L. D-dimer levels were 5.1 (4.2, 12.2) mg/L, of which 29 cases (81%) were ≥4.0 mg/L. The total duration of anticoagulation 3.1 (2.5, 4.2) months. All children received rivaroxaban for 2.7 (2.2, 3.8) months. Of the 36 children, 35 cases were followed up after 3 months of anticoagulant therapy, and 30 cases (83%) showed pulmonary artery thrombus absorption. Finally, follow-up outcome data were available for 34 cases, of which 33 showed complete resolution of thrombus in the affected areas, and 1 showed partial resolution. There were no cases of death, thrombus recurrence or progression, major bleeding events occurred or chronic thromboembolic pulmonary hypertension. Adverse events included hemoptysis in 2 cases and elevated liver enzymes in 4 cases. After the treatment of rivaroxaban, the levels of D-dimer were decreased compared with those before the treatment of PTE (0.3 (0.2, 0.5) <i>vs.</i> 5.1 (4.2, 12.2) mg/L, <i>Z</i>=-7.12, <i>P</i><0.05), and the levels of prothrombin time levels were significantly longer compared with those before the treatment of PTE (3.6 (12.4, 14.9) <i>vs.</i> 13.0 (11.8, 13.6) s, <i>Z</i>=2.34, <i>P</i><0.05). <b>Conclusions:</b> During the course of MPP, the emergence of clinical symptoms such as short of breath, chest pain, hemoptysis, dyspnea or along with elevated D-dimer levels, should raise suspicion for the occurrence of PTE. Rivaroxaban has shown good efficacy and a favorable safety profile.