Surviving Fluid Excess: A Rare Case of Collapsing Glomerulopathy with IgM Kappa Monoclonal Gammopathy of Renal Significance

Introduction: Collapsing glomerulopathy (CG) consists of rapid kidney failure and nephrotic syndrome (NS) which can occur with malignancy. Similarly, monoclonal gammopathy of renal significance (MGRS) is a rare renal failure characterized by clonal plasma or B-cells leading to NS from nephrotoxic monoclonal immunoglobulin deposits in the kidney. Our unique case describes collapsing glomerulopathy in IgM kappa deposition disease causing MGRS. Case Description: A 78-year-old Haitian male with type II diabetes, hypertension, hyperlipidemia and cerebrovascular attack (2019) was referred for poorly controlled hypertension and rising creatinine. Family history included diabetes but no contributing medications or social history. Initial serum creatinine (SCr) of 0.8 mg/dL trended from 1.4 to 4.4 within four months. Urinalysis revealed 100+ protein without hematuria and elevated spot urine microalbumin/Cr of 3484 mg/g and urine protein/Cr of 4.4g. Serum protein electrophoresis (SPEP) with immunofixation (IFE) had peak in gamma region with IgM kappa but normal kappa/lambda ratio. Otherwise hepatitis B/C, HIV, parvovirus, ANCA, and ANA were negative. Albumin trended 3.7 g/dL to 3.2 g/dL, Hgb 12 g/dL to 8.5 g/dL, cholesterol 145 mg/dL to 216 mg/dL and LDL 66 mg/dL to 135 mg/dL. On subsequent appointments, SBP ranged 150s to 220s mmHg with progression of lower extremity edema. Renal biopsy revealed collapsing glomerulopathy with concurrent IgM Kappa deposits. Hematology evaluation with peripheral blood cytology, bone marrow biopsy and PET/CT imaging diagnosed low-grade monoclonal B-cell lymphocytosis CLL type or B- cell clone causing MGRS. He was treated with rituximab however required dialysis initiation. Discussion: MGRS is a disease of the kidney, secondary to plasma or B-cell clonal proliferation, requiring treatment to eradicate the offending clone. When plasma or B-cell clones cannot be identified by lab work and bone marrow testing, kidney biopsy can direct treatment. The rapid progression of these diseases warrants prompt diagnosis and treatment to prevent dialysis and furthermore improve prognosis and mortality in this patient population. The rare occurrence of collapsing glomerulopathy simultaneously with IgM Kappa deposition disease warrants further investigation into MGRS treatment protocols.