AKI in Older Adults: Recognizing the Subtle Signs of a Silent Threat

Introduction: Diagnosing glomerular disease in older adults is challenging due to age-related renal decline that can obscure other clinical manifestations. While common etiologies like infection-related GN are often considered, less typical causes are overlooked. A thorough evaluation can uncover underlying systemic diseases. Case Description: An 82-year-old female with hypertension and CKD stage IIIA presented with a 3 week history of dysuria,dyspnea, and nonproductive cough. Labs showed leukocytosis, hyponatremia (Na 126 mmol/L), and AKI (creatinine 1.56 mg/dL; baseline 1.1–1.2). Urine microscopy demonstrated muddy brown casts.Despite treatment of the infection and supportive care for the AK, the patient exhibite persistent hematuria and proteinuria (UACR 1373 mg/g, UPCR 2000 mg/g) prompted further workup. Repeat urine microscopy revealed dysmorphic RBCs, low serum C3/C4, and a monoclonal IgM kappa on SPEP. Renal biopsy showed membranoproliferative glomerulonephritis with monoclonal IgM kappa and C3 deposits on immunofluorescence. Bone marrow biopsy revealed small B-cell non-Hodgkin lymphoma consistent with an indolent B-cell lymphoma. She was started on rituximab by oncology and her kidney function improved. Discussion: This case emphasizes the importance of considering monoclonal gammopathy of renal significance (MGRS) in older adults with unexplained decline of renal function and hematuria. Kidney biopsy was pivotal in revealing MPGN with monoclonal deposits, prompting hematologic evaluation and early diagnosis of B-cell lymphoma. In elderly patients with persistent hematuria and proteinuria, a comprehensive evaluation including serologies and kidney biopsy can reveal underlying systemic diseases, enabling early treatment that could improve patient and renal outcomes.