Abstract: PUB312
Codeposition of Vancomycin and Light Chains in Tubular Casts: Dual-Composition Cast Nephropathy in Multiple Myeloma
Session Information
Category: Pathology and Lab Medicine
- 1800 Pathology and Lab Medicine
Authors
- Lee, Benjamin J., Houston Methodist Hospital, Houston, Texas, United States
- Fakhri, Nibras, Banner - University Medical Center Phoenix, Phoenix, Arizona, United States
- Gaber, Lillian W., Houston Methodist Hospital, Houston, Texas, United States
- Truong, Luan D., Houston Methodist Hospital, Houston, Texas, United States
Introduction
A 77-year-old man with stage 3a CKD and kappa myeloma presented with AKI while on IV antibiotics for septic arthritis. Four years prior, he developed dialysis-requiring AKI from biopsy-proven light-chain (LC) cast nephropathy, prompting a myeloma diagnosis. After chemotherapy (CyBorD), he achieved sufficient renal recovery to stop dialysis after four months.
Case Description
The patient re-presented with left knee pain two weeks after arthroplasty revision. Although the joint aspirate did not yield pathogenic bacteria, vancomycin and cefepime were started due to a past history of MSSA and Pseudomonal infections. Serum creatinine (Cr) was 2.9 mg/dL (baseline 1.4 mg/dL), with a random vancomycin level of 28 ug/mL. Vancomycin was discontinued but Cr continued to rise, peaking at 4.2 mg/dL 16 days later. Although in partial remission for myeloma on an investigational agent, serum free kappa LC had risen to 2,950 mg/dL (kappa-lambda ratio 306). Renal biopsy showed tubular casts, some containing both vancomycin and kappa LC (Image), and acute interstitial nephritis. With vancomycin withdrawal, IV hydration, and steroids, Cr improved to 1.9 mg/dL. Due to worsening LC burden and these biopsy findings, he was transitioned to a different clinical trial for myeloma treatment.
Discussion
While cast nephropathy is classically caused by monoclonal LC, concurrent tubular injury from other agents should not be overlooked. This case uniquely demonstrates co-deposition of vancomycin and monoclonal LC in a single cast. Although cast nephropathy presenting with other myeloma-associated renal findings has been described, dual-composition casts are a novel finding that has not been previously reported.
A. LM (silver methenamine stain): upper tubular cast has a black vancomycin core surrounded by red light chains; lower cast is composed entirely of light chains. B. IF: upper cast shows kappa light chains surrounding a negative core; lower cast is uniformly kappa-positive. No lambda light chains detected. C. EM: dual-composition cast with a pathognomonic concentrically laminated vancomycin core surrounded by amorphous electron-dense material typical for light chains.