Light Chain Multiple Myeloma Presenting as Acute Kidney Injury in a 57-Year-Old Man with Concurrent Norovirus Gastroenteritis: A Case Report
Renal impairment is a common and serious complication of multiple myeloma (MM), affecting 20-50% of patients at diagnosis, with light-chain cast nephropathy representing the leading cause of severe acute kidney injury (AKI). Excess monoclonal free light chains precipitate within renal tubules, causing obstruction, inflammation, and rapid loss of kidney function. Because AKI often occurs alongside more common conditions such as dehydration or infection, the diagnosis of MM may be delayed. We present a rare case in which norovirus gastroenteritis served as the precipitating event that unmasked previously undiagnosed light-chain multiple myeloma with biopsy-proven cast nephropathy.
Materials and Methods/Case Presentation/Objective: A 57-year-old man with hypertension, hyperlipidemia, prior cerebrovascular accident, and non-obstructive coronary artery disease presented with 3-4 days of profuse diarrhea, vomiting, left-sided abdominal pain, and dark stools. Laboratory evaluation revealed severe AKI with a serum creatinine of 17.5 mg/dL, BUN of 104 mg/dL, metabolic acidosis, proteinuria, and hematuria. Gastrointestinal pathogen testing was positive for norovirus. Despite an apparent infectious etiology, the severity of renal dysfunction prompted further evaluation, which demonstrated markedly elevated serum free kappa light chains (11,347.4 mg/L), a kappa/lambda ratio of 766.7, and an M-protein spike. Bone marrow biopsy confirmed kappa light-chain multiple myeloma with approximately 80% marrow involvement, and cytogenetics demonstrated trisomy 15, consistent with Revised International Staging System (R-ISS) stage III disease. Once blood pressure was controlled, renal biopsy confirmed kappa-restricted cast nephropathy with minimal chronic tubular damage. The patient required hemodialysis, received two sessions of plasmapheresis, and was started on dexamethasone and cyclophosphamide. He remained dialysis-dependent at discharge with close nephrology and hematology follow-up.
Results/Description/Main Outcome Measure(s):
Cast nephropathy is a myeloma-defining event and the most frequent cause of dialysis-dependent renal failure in MM. Volume depletion from norovirus likely acted as a "second hit," increasing tubular free light-chain concentration and accelerating cast formation, thereby transforming an otherwise occult plasma cell disorder into fulminant renal failure. This case illustrates that persistent or disproportionate AKI should not be attributed solely to dehydration or infection, even when an infectious trigger is identified. Renal biopsy played a pivotal role by confirming the specific pattern of injury and supporting urgent initiation of clone-directed therapy. Although extracorporeal free light-chain removal remains controversial, studies such as the MYRE trial have not demonstrated improved short-term dialysis independence with high-cutoff hemodialysis. Current evidence therefore supports prompt initiation of plasma cell-directed chemotherapy as the cornerstone of management, while plasmapheresis should be considered selectively and should never delay definitive treatment.
Conclusion(s).: This case emphasizes the importance of maintaining a high index of suspicion for plasma cell dyscrasias in patients with AKI that is disproportionate to the apparent clinical insult or fails to improve with correction of reversible causes. Common illnesses such as norovirus gastroenteritis may precipitate or mask underlying myeloma-related kidney disease. Early recognition, renal biopsy when appropriate, and rapid initiation of clone-directed therapy are critical to maximizing the likelihood of renal recovery and improving patient outcomes.
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References: Verstraeten, T., Jiang, B., Weil, J. G., & Lin, J. H. (2016). Modelling Estimates of Norovirus Disease in Patients with Chronic Medical Conditions. PLOS, 11(7), e0158822. https://doi.org/10.1371/journal.pone.015882
