Steroid-resistant nephrotic syndrome as paraneoplastic syndrome of Waldenström macroglobulinemia: a case report.

Reports of glomerulonephritis associated with lymphoproliferative disorders are common, but reports of minimal change disease (MCD) accompanying non-Hodgkin's lymphoma are rare. Here, we present a case of a 45-year-old woman diagnosed with primary Waldenström's macroglobulinemia (WM) during MCD treatment. Her kidney biopsy revealed endothelial cell injury in parts of the MCD. Subsequently, she developed steroid-resistant nephrotic syndrome and temporary acute kidney injury, requiring dialysis. Remission of the nephrotic syndrome was achieved after initiating combination therapy with bendamustine and rituximab for WM. The renal histological findings and treatment course suggest a causal relationship between MCD and WM in this case. The pathogenesis of MCD associated with WM may involve the release of glomerular permeability factors derived from B lymphocytes. Although mild WM is often managed with observation, steroid-resistant nephrotic syndrome associated with WM should raise suspicion of a paraneoplastic syndrome, necessitating active chemotherapy targeting WM as a critical treatment approach.