Medium cut-off hemodialysis in multiple myeloma-associated cast nephropathy: A single-center experience.

BACKGROUND: Myeloma cast nephropathy (CN) is a severe complication of multiple myeloma and a frequent cause of dialysis-dependent acute kidney injury (AKI). High circulating free light chains (FLC) contribute to tubular injury, and strategies aimed at accelerating their reduction have been proposed. Medium cut-off (MCO) membranes allow enhanced clearance of middle molecules, including FLC. Clinical data regarding their implementation in routine practice remain limited. The aim of this study was to describe our institutional experience following the introduction of MCO hemodialysis in patients with dialysis-dependent CN. MATERIALS AND METHODS: We conducted a retrospective single-center case series including consecutive patients treated between February 2024 and December 2025. Eligible patients had dialysis-dependent AKI due to presumed or biopsy-proven CN and were managed according to a predefined protocol combining anti-myeloma therapy and intensive MCO hemodialysis (Theranova 500), consisting of eight 6-hour sessions within the first 10 days when clinically feasible. Serum FLC levels were measured before each session. RESULTS: Six patients were included. Baseline FLC levels ranged from 1,550 to 30,000 mg/L. A marked early decline in circulating FLC was observed during the intensive MCO phase, with 4 patients achieving > 80% reduction. Treatment interruptions due to clinical instability, frequently associated with infectious complications, occurred in several cases. Renal trajectories were heterogeneous, and dialysis independence was achieved in 3 patients. CONCLUSION: This case series describes the real-world implementation of MCO hemodialysis in dialysis-dependent CN. Although substantial early FLC reduction was observed, renal recovery varied and appeared to be influenced by multiple clinical factors.