A paraneoplastic membranoproliferative glomerulonephritis with isolated C3 deposits associated with hairy cell leukaemia.

We describe a 35-year-old woman who presented with proteinuria and microscopic haematuria. Blood tests revealed a low C3 complement level, with no evidence of cryoglobulin. Renal biopsy showed a Type 1 membranoproliferative glomerulonephritis (MPGN) with isolated C3 deposits on immunofluorescence study. Bone marrow aspirate, done for monocytopenia, was consistent with a diagnosis of hairy cell leukaemia (HCL). Both haematological and nephrological diseases completely responded to treatment with cladribine, strongly suggesting that the renal disease was a paraneoplastic syndrome. To our knowledge, this is the first report of a non-cryoglobulinaemic MPGN associated to HCL.