Membranous nephropathy and thrombotic thrombocytopenic purpura treated with rituximab

A 43-year-old black male was brought to hospital with complaints of confusion and fever. He was noted to have petechial lesions, thrombocytopenia (platelet count 7,200/ml), schistocytes on peripheral smear, and serum creatinine 1.7 mg/dl (150.28 mu mol/L). He was diagnosed to have thrombotic thrombocytopenic purpura (TTP) and started on high dose IV steroids and plasmapheresis. Attempts at steroid withdrawal following plasmapheresis were unsuccessful as his platelet count started to decrease. He subsequently was started on rituximab given as 4 weekly infusions. The platelet count normalized after 2 doses of rituximab. A kidney biopsy performed to evaluate proteinuria (10.24 gms/24 hr) revealed membranous nephropathy (MN), with organized obliterative arteriopathy consistent with thrombotic microangiopathy. Upon completion of the treatment, proteinuria decreased to 1.67 gm/24hr. Recent studies indicate that patients with TTP have an inhibitory (auto) antibody to von Willibrand factor cleaving protease (ADAMTS 13). Considerable evidence also exists that idiopathic membranous nephropathy is an autoimmune disease. Rituximab, a monoclonal chimeric antibody directed against CD20 antigen present on B cells, selectively depletes B cells and has been used with success in both diseases. Though evidence for a direct pathogenetic relationship between TTP and MN is lacking, the two entities are more likely related to autoantibodies induced by activation of B cells. For our patient with this rare disease combination rituximab therapy was one treatment solution to two diseases.