Acute Thrombotic Microangiopathy and Cortical Necrosis Following Administration of Alemtuzumab: A Case Report

Alemtuzumab, a humanized monoclonal antibody that targets CD52 antigens on lymphocytes and monocytes, has shown efficacy in preventing relapse in relapsing-remitting multiple sclerosis. Despite known severe (yet rare) renal side effects such as anti-glomerular basement membrane disease and membranous glomerulopathy, to our knowledge, alemtuzumab has never been documented to cause drug-induced thrombotic microangiopathy. We describe a 39-year-old woman with relapsing-remitting multiple sclerosis who developed acute kidney injury requiring renal replacement therapy after 1 dose of alemtuzumab, as well as microangiopathic hemolytic anemia and thrombocytopenia. Pathologic examination of a kidney biopsy specimen demonstrated extensive cortical necrosis and arteriolar fibrin thrombi with nonspecific immunofluorescence staining of immunoglobulin M and C3 and absence of immune deposits on electron microscopy. These findings were consistent with the diagnosis of acute thrombotic microangiopathy. She received dexamethasone and underwent plasmapheresis, which was unsuccessful at removing alemtuzumab. The patient received renal replacement therapy for approximately 7 weeks, followed by slow recovery of kidney function that returned close to her baseline.