Rituximab in Patients With Relapsed or Refractory TTP-HUS

Inclusion Criteria: * any patient 18 years or older diagnosed with relapsed or refractory TTP-HUS requiring therapy Exclusion Criteria: * alternate cause of hemolytic microangiopathy (evidence of DIC, malignant hypertension, vasculitis, anti-phospholipid antibody syndrome, post-partum acute renal failure) * congenital or familial TTP * TTP occuring post-stem cell, bone marrow, or solid organ transplant * drug-induced TTP * pregnancy or breast-feeding * history of hepatitis B or C infection * prior rituximab treatment * active or metastatic cancer * other causes of thrombocytopenia such as ITP, myelodysplastic syndrome, confirmed or suspected drug-induced thrombocytopenia * refusal to receive blood products * hypersensitivity to blood products, plasma products, murine proteins, or any component of the Rituximab formulation * geographic inaccessibility * co-morbid illness limiting life expectancy to less than 2 months independent of TTP * failure to provide written informed consent