Case Report Focal Segmental Glomerulosclerosis in Waldenstr¨ om’s Macroglobulinemia Akshee Batra , Shatha Herz Allah, and Bijin Thajudeen Department of Nephrology, Banner University of Arizona Medical Center, 1501 North Campbell Ave, Tucson, AZ, USA Correspondence should be addressed to Bijin ajudeen; bijint@gmail.com Received 5 July 2020; Revised 7 August 2020; Accepted 17 August 2020; Published 27 August 2020 Academic Editor: Bernard G. Jaar Copyright © 2020 Akshee Batra et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Renal involvement in Waldenstr¨ om’s macroglobulinemia is a rare manifestation. Although most renal involvement is due to monoclonal immune deposits, pathology can also be unrelated to it. Here, we describe a 68-year-old female with a history of Waldenstr¨ om’s macroglobulinemia who presented with generalized edema and nephrotic range proteinuria. A renal biopsy showed findings consistent with focal segmental glomerulosclerosis. Treatment with oral prednisone leads to the resolution of proteinuria. is case highlights the importance of identifying pathology that might not be directly related to monoclonal gammopathy, which could have implications on the management. 1. Introduction Waldenstr¨ om’s macroglobulinemia (WM) is a lympho- proliferative disorder involving B cells characterized by an IgM monoclonal protein >1g/dl and 10% lympho- plasmacytic infiltrate in the bone marrow [1]. Kidney disease is a common presentation of WM usually charac- terized by IgM deposits along the glomerular basement membrane (GBM), infiltration of the interstitium, or am- yloidosis [1, 2]. However, occasionally the pathology could be unrelated to the immunoglobulin deposition (Tables 1 and 2). Here, we report a case of focal segmental glo- merulosclerosis (FSGS) in a patient with WM. According to our knowledge, there is only one other reported case of FSGS in WM [1]. 2. Case Report A 68-year-old female presented to the outpatient clinic with complaints of lower extremity edema for four weeks. Her past medical history was significant for lympho- plasmacytic lymphoma with IgM monoclonal gammop- athy or WM. Since the criteria for treatment were not met, she did not receive any treatment for WM. Her home medications included omeprazole and ferrous sulfate. Her vitals showed a temperature of 98 ° F, blood pressure of 136/78 mmHg, pulse rate of 84/minute, respiratory rate of 16/min, and body mass index of 22.35 kg/m 2 . e rest of the physical examination was unremarkable except for 2+ edema of the lower extremities. Laboratory studies yielded the following values: hemoglobin 8.3 g/dl, white blood cell count 14400/mm 3 , platelet count 496000/mm 3 ,bloodurea nitrogen 13 mg/dl, creatinine 0.6 mg/dl, calcium 8.5 gm/ dl, erythrocyte sedimentation rate (ESR) 94 mm/1st hour, LDH 340 IU/I, and total protein 7.5 g/dl with albumin 3.9 g/dl. Urine sediments contained few erythrocytes and hyaline casts. e spot protein/creatinine ratio was 16.2gm/gm creatinine, and the albumin-to-creatinine ratio was 9.9 gm/gm creatinine. Serum immunoelectro- phoresis showed IgM 1693 mg/dl, IgG 453 mg/dl, and IgA 23mg/dl. Serum immunofixation revealed monoclonal IgM kappa light chains. e concentration of serum kappa and lambda light was 73.74mg/L and 2.38mg/L, re- spectively. e ratio of kappa to lambda was 30.98. Pe- ripheral blood flow cytometry revealed a monocytic kappa light-chain-restricted B-cell population. Cryoglobulins were absent. All serologies, including complements, ANA, anti-dsDNA, ANCA, HIV, and hepatitis panel, were negative. A renal biopsy was performed. Light microscopy showed glomeruli with thin and delicate capillary loops, Hindawi Case Reports in Nephrology Volume 2020, Article ID 8895705, 3 pages https://doi.org/10.1155/2020/8895705