De Novo Lupus Anticoagulant-Positive Catastrophic Antiphospholipid Syndrome With Multiorgan Microvascular Failure: A Thrombotic Cascade Beyond Control.

Catastrophic antiphospholipid syndrome (CAPS) is an uncommon but life-threatening manifestation of antiphospholipid syndrome characterized by rapidly progressive multiorgan failure due to diffuse small-vessel thrombosis. Early recognition is challenging, particularly in patients without prior obstetric morbidity or established autoimmune disease. We report a 38-year-old woman who presented with acute limb ischemia, respiratory distress, thrombocytopenia, and acute cerebral infarcts. Laboratory evaluation revealed lupus anticoagulant positivity, reduced protein C, protein S, and antithrombin III levels, and elevated D-dimer. Imaging demonstrated diffuse distal arterial narrowing without large-vessel occlusion, bilateral pulmonary ground-glass opacities, and multiple lacunar infarcts. Skin biopsy showed occlusive arteriolopathy without evidence of vasculitis, and direct immunofluorescence was negative. A heterozygous factor V Leiden mutation was detected. A diagnosis of microvascular thrombotic disease consistent with CAPS was made after the exclusion of vasculitis and embolic causes. Despite prompt anticoagulation and corticosteroid therapy, she developed progressive multiorgan dysfunction and died. This case highlights the importance of recognizing CAPS as a predominantly microvascular thrombotic disorder that may present without prior features of antiphospholipid syndrome. The coexistence of inherited thrombophilia may act as a prothrombotic amplifier and contribute to a fulminant clinical course.