Compound Heterozygous Protein C Deficiency Presenting With Splenic Infarction After COVID-19: A Case Report.

Congenital protein C deficiency is a rare autosomal recessive disorder that predisposes patients to severe thrombosis due to markedly reduced protein C activity. Although primarily associated with venous events, an increased risk of arterial thrombosis is also recognized, particularly in severe cases. We report the case of a 17-year-old male patient with compound heterozygous protein C deficiency who developed venous thromboembolism (VTE) after coronavirus disease 2019 (COVID-19) and subsequently experienced splenic infarction despite anticoagulant therapy. Diagnosed shortly after birth following neonatal purpura fulminans, he had been maintained on long-term warfarin therapy. The patient presented with fever and cough and was diagnosed with COVID-19 by antigen testing. Soon after symptom onset, he developed right thigh pain with rapidly expanding ecchymosis, leading to a diagnosis of recurrent VTE. Intravenous heparin and fresh frozen plasma (FFP) were initiated. Although his symptoms and coagulation markers improved by day 10, he developed sudden abdominal pain on day 11, and a contrast-enhanced CT scan revealed a partial splenic infarction. Anticoagulation was intensified, and he subsequently recovered without sequelae. COVID-19 can precipitate both venous and arterial thrombosis through endothelial injury and inflammation. This case illustrates that thrombotic events may occur even after apparent clinical and biochemical improvement, emphasizing the need for careful monitoring and individualized anticoagulation strategies in patients with protein C deficiency during and after COVID-19.