#6333 LARGE B CELL RENAL INFILTRATION IN A PATIENT WITH WALDESTRöM MACROGLOBULINEMIA: A CASE REPORT
Authors: Allegretta Federica , Gesualdo Campolo , Antonella Olivieri , Ercoletti Sarah , Allinovi Marco , Caroti Leonardo , Antognoli Giulia , Santi Raffaella , Novelli Luca , Ravaglia Fiammetta 
Published: June 2023

Abstract

Background and Aims
Waldeström Macroglobulinemia (WM) is a clinicopathologic entity demonstrating lymphoplasmacytic lymphoma (LPL) in the bone marrow with an IgM monoclonal gammopathy in the blood. Only 15% of patients with WM may develop a renal insufficiency due to either glomerular or tubulointerstitial pathologies. Most common findings include deposits of IgM in the glomerular basement membrane and infiltration of lymphocytes or plasmacytoid cells; light chain cast nephropathy; nephrotic syndrome led by AL amyloid deposition; immune-mediated glomerulonephritis (typically due to IgM deposition or cryoglobulinemia) and non-amyloid nephrotic syndrome (minimal change-like). Moreover, WM may evolve in hematological malignancies with renal localization. Therefore, a renal biopsy may be needed in patients who have recent unexplained renal dysfunction.

Method
A 72-year-old male with a history of WM is referred to our nephrology center for declining renal function. He had been diagnosed with Waldeström Macroglobulinemia IgM Kappa 4 years prior to presentation, at onset serum protein electrophoresis showed an M spike of 4900. After diagnosis confirmation, he underwent treatment with 6 cycles of rituximab and bendamustine resulting in a complete response and M spike at serum protein electrophoresis lowering to 23. At WM diagnosis his renal function was normal, he had no proteinuria nor urinary Bence-Jones. His medical background also included hypertension and diabetes mellitus type 2, both in good pharmacologic control and Sars-Cov2 infection. Two years later, we witnessed to progressive presentation of anemia, fatigue and cough along with hepatomegaly, axillary lymphomegaly, pulmonary basal thickenings and IgM levels elevation. Serum creatinine was 1,47 mg/dl, proteinuria 1,75 g/die, no urinary Bence-Jones proteinuria. A renal ultrasound showed poor cortico-medullary differentiation in both kidneys and a left kidney slightly bigger than the other one. Respiratory symptoms and pulmonary thickenings persisted after antibiotics therapy, also cytology and culturing exams performed on broncho-alveolar lavage resulted negative. To exclude a possible relapse of WM, a BOM and a lymphnodal mass biopsy were performed. Both exams showed no disease progression. Due to lack of WM progression, the patient is referred to renal biopsy execution.

Results
Renal biopsy showed morpho-phenotypic findings for localization of mainly large B peripherical cells, partial plasmocytic differentiation and high proliferation levels. Further exams revealed a double monoclonal component IgM Kappa with normal Kappa/Lambda, also a total Body TC was performed, and it evidenced a possible renal and pulmonary lymphoproliferative disease involvement. In the figure an image of the patient's renal biopsy showing IgM immunofluorescence. Our patient is still fulfilling all the supplementary analysis needed to evaluate the best therapeutic strategies. We also reviewed all renal biopsies performed in our center in patients with hematological diseases in the last 10 years and a neoplastic renal infiltration was documented in just 6 cases out of 650 biopsies.

Conclusion
Although lymphomatous infiltration of the kidney in WM is a rare event, it should be considered in patients presenting with abnormal renal function. It is important during follow-up to monitor kidney function in patients with plasma cell dyscrasias, even if patients appear to have stable lymphoproliferative disease.