Rare pediatric multi-system thrombosis post-COVID-19: a three-year follow-up case report and narrative review on rivaroxaban for long-term management.

This retrospective study presents a 10-year-old male with multi-systemic venous thromboembolism (VTE) secondary to COVID-19, including right ventricular thrombus(40 mm × 18 mm), bilateral iliac vein thrombosis, pulmonary embolism, and renal vein thrombosis. The child presented with fever, abdominal pain, and elevated inflammatory markers (CRP 222.72 mg/L, WBC 22.41 × 10⁹/L). Imaging confirmed extensive thrombi in the right ventricle, pulmonary arteries, and lower extremities. Anticoagulation with rivaroxaban (10 mg QD) was initiated alongside anti-infective and anti-inflammatory therapies. Over a 3-year follow-up, thrombus burden significantly regressed, with D-dimer decreasing from 73 430 µg/L to 290 µg/L, and no recurrence or bleeding complications were observed. Coagulation parameters (PT, APTT) stabilized within therapeutic ranges. This case suggests the efficacy and safety of rivaroxaban in long-term management of multi-system VTE in pediatric patient, especially in cases of COVID-19-associated hypercoagulability. The primary clinical outcomes were the resolution of thrombus burden as evidenced by imaging and the absence of bleeding complications or recurrence during the follow-up period. The findings align with emerging evidence supporting direct oral anticoagulants (DOACs) in children, emphasizing individualized dosing and long-term management. Further studies are warranted to validate DOACs' role in pediatric thrombosis, especially in the context of viral infections.