Waldenstrom's macroglobulinemia and nephrotic syndrome with membranous nephropathy

Renal complications of Waldenstrom's macroglobulinemia (WM) are rarely observed. Nephrotic syndrome in association with WM has most often been secondary to amyloidosis. This article reports a case of WM with nephrotic syndrome as a result of membranous nephropathy with immunoglobulin M (IgM) deposition. A 44-year-old male diagnosed with WM 4 years previously, presented with heavy proteinuria (7.8 g/24 h). Kidney biopsy revealed expanded mesangium, thickened capillary loops and epimembranous spikes, with no significant interstitial inflammation or thickened tubular basement membranes. Immunofluorescence examination demonstrated strong granular staining of IgM and l light chains, with weaker C3 and C1q staining. Electron microscopy showed many subepithelial dense deposits, and fewer large subendothelial dense deposits. Treatment was directed at the patient's WM with maintenance rituximab and fludarabine. Subsequently, decreases were seen in both the patient's serum IgM and serum viscosity. With therapy for WM and the addition of an angiotensin receptor blocker, the patient's proteinuria also improved, from 7.8 g to 4.8 g/24 h. The patient continued to follow up with his hematologist and in 2009 creatinine was 1 mg/dl (76.26 mu mol/l), with a 24 h urine protein excretion of 0.159 g.