Abstract: PUB570
Immunotactoid Glomerulopathy in a Patient with Monoclonal B-Cell Lymphocytosis: A Rare Finding
Session Information
Category: Trainee Case Report
- 1202 Glomerular Diseases: Immunology and Inflammation
Authors
- Kanu, Obiajulu, UNC Hospitals, Nephrology, Chapel Hill, North Carolina, United States
- Derebail, Vimal K., University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
- Singh, Harsharan Kaur, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
- Coombs, Catherine C., University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
- Saha, Manish K., UNC Kidney Center, Chapel Hill, North Carolina, United States
Introduction
Monoclonal B-cell Lymphocytosis (MBL) and glomerular diseases are a rare association. We present an unusual case of an adult male who developed nephrotic syndrome and was found to have immunotactoid glomerulopathy secondary to MBL.
Case Description
A 54-year-old male with history of well-controlled hypertension on lisinopril was evaluated for significant bilateral leg swelling. Laboratory evaluation was remarkable for 24-hr proteinuria of 8g/day, eGFR of 85 ml/min/1.73m2, and serum albumin 2.5g/dl. Autoimmune serologies, serum free light chains, serum immunoelectrophoresis, and imaging studies of the thorax and abdomen were unremarkable.
Renal biopsy showed thickened capillary walls by light microscopy with IgG2 kappa monoclonal glomerular capillary wall deposits by immunofluorescence microscopy. Electron microscopy showed widespread foot process effacement and intramembranous deposits with a microtubular substructure, organized in parallel bundles, and measuring ~25nm in diameter.
Flow cytometry of the peripheral blood showed very low-level clonal lymphocytes (1.4% of circulating white blood cells; 128 cells/microliter). Bone marrow aspiration revealed CD5-positive B-cell lymphoid proliferation with predominantly small lymphoid cells comprising 20% of marrow cellularity with a phenotype most compatible with MBL.
The patient was started on bendamustine and rituximab (BR). After 6 cycles of BR regimen, repeat bone marrow biopsy showed 0.01% involvement and clinical symptoms improved with reduction in proteinuria to 1.6gm, normalization of serum albumin and preserved renal function.
Discussion
Immunotactoid glomerulopathy is characterized by glomerular capillary and/or mesangial organized deposits with a microtubular substructure. 40-50% of patients develop end stage renal disease within few years of diagnosis, underscoring the need for early diagnosis and treatment. Our case in a patient with MBL highlights the importance of evaluation for an underlying lymphoproliferative disorder with appropriate imaging studies, peripheral flow cytometry and bone marrow biopsy even in the absence of a peripheral paraproteinemia. An early target-directed therapy towards B-cell or plasma-cell clone may result in preservation of renal function.