Waldenström macroglobulinemia presenting as nephrotic syndrome: Renal heavy and light chain amyloidosis

[摘要] A 71-year-old woman presented with nephrotic syndrome with preserved renal function. Immunofixation of the peripheral blood showedimmunoglobulin M (IgM) κ paraproteinemia of 4.1 g/L with free κ lightchain of 10.0 mg/dl and free λ light chain of 26.9 mg/dl, κ/λ ratio of0.37 and differential free light chain (dFLC) of 16.9 mg/dl. Bone marrow biopsy demonstrated a B-cell infiltrate with plasmacytoid differentiation, negative for CD5, CD23, and CD10, monoclonal for lambda,and presence of a MYD88 L265P mutation, consistent with Waldenström macroglobulinemia (WM). Congo red stain was negative. CTscan of the neck/thorax/abdomen showed neither lymphadenopathynor organomegaly. Kidney biopsy was performed and showed subtle enhancement of mesangial areas by light microscopy (Figure 1A),suggestive of depositions, with immunofluorescence demonstratingIgM heavy chain as well as λ light chain deposition (Figure 1C,D).Electron microscopy showed fibrils with a thickness of 9 nm consistent with amyloid deposition (Figure 1B).

[关键词] amyloidosis;M. Waldenström;nephrotic syndrome