Thrombotic microangiopathy in patients with phosphatidylserine dependent antiprothrombin antibodies and antiphospholipid syndrome

Thrombotic microangiopathy (TMA) is a rare disorder characterized by microvascular thrombosis. TMA has been reported in patients with antiphospholipid antibodies and/or antiphospholipid syndrome but its pathogenesis is not clarified. We present two patients with TMA associated with IgG phosphatidylserine dependent antiprothrombin antibodies (aPS/PT). CASE 1: A 44-year-old Japanese female with systemic lupus erythematosus (SLE) and positive lupus anticoagulant (LA) was started on ticlopidine after having stroke. Four weeks later she developed TMA. IgG/M/A anticardiolipin antibodies (aCL) were negative, but strong positive IgG aPS/PT were detected. CASE 2: A 32-year-old Russian female with SLE was admitted because of hypertension, renal insufficiency and proteinuria at 14 weeks of pregnancy. She developed TMA after surgical abortion. IgG aPS/PT and LA were strongly positive but IgG/M/A aCL were negative. Neither case had von Willebrand factor cleaving protease (ADAMTS-13), suggesting that TMA in those patients was associated with thrombophilia rather than insufficient ADAMTS-13. Both patients were successfully treated with a series of plasma exchange.