Abstract: Objective To explore ways to monitor coagulation functions of warfarin in children with chronic diseases amid COVID-19. Methods One case of Kawasaki disease with a giant coronary aneurysm was reported, who had developed non-traumatic spontaneous lower extremity muscle hemorrhage during anticoagulation with warfarin and aspirin but without regular follow-up amid COVID-19. Response measures against the use of warfarin in children with chronic diseases during the pandemic were explored. Results Because of the COVID-19 pandemic, the child failed to be followed up regularly, resulting in coagulation dysfunction and serious non-invasive spontaneous muscle hemorrhage. After blood transfusion and improvement of coagulation function, the bleeding was stopped and the lower limb activity restored. Conclusion Warfarin is a commonly-used anticoagulant against Kawasaki disease combined with a coronary artery aneurysm, but excessive or insufficient anticoagulation can cause serious complications. Therefore, the INR of patients needs to be monitored. Clinicians should use anticoagulants with caution during the epidemic and remain alert to bleeding in unusual locations.

Key words: warfarin, COVID-19, Kawasaki disease, spontaneous muscle hemorrhage