Abstract
Waldenström macroglobulinemia (WM) is a rare CD20-positive B-cell non-Hodgkin lymphoma. It is characterized by lymphoplasmacytic infiltration in the bone marrow and abnormal monoclonal IgM secretion. WM complicated by renal amyloidosis is uncommon but associated with rapid progression of organ damage. Accurate identification of pathogenic factors and individualized treatments are essential to improve prognosis. This paper reports the case of a 75-year-old female who initially presented with facial edema and bilateral lower-extremity edema lasting 2 days. Additional symptoms included foamy urine, frequent urination, and urgency. Laboratory tests revealed significant proteinuria (24-h urinary protein, 6.11 g), hypoalbuminemia (serum albumin, 20.07 g/L), and impaired renal function (serum creatinine, 129.90 μmol/L; eGFR, 45.2 mL/min/1.73 m(2)). Immunofixation electrophoresis detected monoclonal IgM-λ immunoglobulin in both serum and urine. Bone marrow biopsy demonstrated clonal lymphoplasmacytic infiltration (32%), and genetic testing revealed a positive MYD88-L265P mutation (mutation frequency, 28.5%). Renal biopsy indicated diffuse deposition of λ light chains predominantly in the glomerular mesangium. Ultrastructural examination revealed amyloid fibrils, confirming the diagnosis of AL λ - type amyloid nephropathy. Chemotherapy with rituximab, cyclophosphamide, and dexamethasone (RCD regimen), combined with symptomatic supportive therapy, resulted in temporary improvement of clinical symptoms and laboratory parameters. However, the disease progressed rapidly. The patient died on Jan 28, 2024, approximately 3 months after discharge, due to multiple organ failure involving cardiac, renal, and respiratory dysfunction. Based on relevant literature and the Chinese Expert Consensus on Diagnosis and Treatment of Lymphoplasmacytic Lymphoma (LPL)/WM (2022 Edition) [Abstract 3], this paper discusses diagnostic criteria, differentiation of pathogenic components, treatment strategies, and prognostic factors. These findings may provide clinical guidance for similar rare cases.