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.