Diagnosing and Managing Paradoxical Deep Vein Thrombosis in a Patient With Congenital Afibrinogenemia

Congenital afibrinogenemia, classically a bleeding disorder, can paradoxically predispose to thrombosis, potentially due to disruptions in fibrin-mediated thrombin clearance and plasmin activation. A young man with reported congenital afibrinogenemia presented with extensive deep vein thrombosis in the setting of undetectable fibrinogen and deceptively low D-dimer, revealing the limitations of fibrin-dependent assays. Management required carefully balanced anticoagulation alongside fibrinogen replacement with subsequent genetic confirmation of a homozygous FGB pathogenic variant. He completed 3 months of therapy with clinical improvement and residual chronic thrombotic changes, emphasizing the need for heightened vigilance and individualized anticoagulation strategies in this population.