Two Types of Renovascular Lesions in Lupus Nephritis with Clinical Thrombotic Thrombocytopenic Purpura

Renovascular lesions of lupus nephritis (LN) were classified into five categories by D'Agati in Heptinstall's Pathology of the Kidney, with thrombotic microangiopathy (TMA) and clinical thrombotic thrombocytopenic purpura (TTP) being combined. We encountered 2 cases with histological LN (class III and lass V), and they presented with clinical features of TTP, such as acute renal failure, microangiopathic hemolytic anemia, thrombocytopenia, fever, and central neurologic symptoms. Immunosuppressive therapy with plasmapheresis was performed in both patients. Case 1 progressed to end-stage renal failure requiring dialysis and died, while case 2 responded to treatment. In case 1, small renal arteries showed positive mural staining for IgG and C3, while intraluminal material was negative for IgG and C3 [although it was positive for phosphotungstic acid-hematoxylin (PTAH), indicating fibrin deposition]. In case 2, small renal arteries showed mural staining for IgG, C1q, and C3, with the intraluminal material also being positive for these immunoglobulins, but negative for PTAH. These cases suggest that immunosuppressive therapy with plasmapheresis can control LN when intravascular thrombosis is related to immune complexes associated with activation of the early complement components C1q and C3. In contrast, immunosuppressive therapy with plasmapheresis may not be effective when intravascular thrombosis is unrelated to these factors and involves fibrin deposition. Accordingly, in LN patients with clinical features of TTP, we report two types of renovascular lesions, in addition to typical vascular change of TMA with no immune deposits seen in nonlupus patients.