Proliferative glomerulonephritis and mantle cell lymphoma: a rare association.

Renal involvement in mantle cell lymphoma (MCL) is rare. We present the case of a man followed for MCL presented with acute kidney injury and positive antineutrophil cytoplasmic antibody (ANCA) type anti proteinase 3 (PR3). He was treated as for a rapidly progressing glomerulonephritis with cyclophosphamide and methylprednisolone followed by oral prednisone. Renal biopsy revealed diffuse endocapillary proliferation and segmental extracapillary proliferation in four glomeruli. Immunohistochemistry confirmed the renal invasion of lymphomatous cells. He started improving his renal function shortly after starting treatment. The coexistence of renal MCL infiltration, extracapillary proliferation and ANCA positive is exceptional. © BMJ Publishing Group Limited 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.