Clinicopathological predictors of renal outcomes in light chain cast nephropathy: A multicenter retrospective study.

Current IMWG guidelines suggest renal biopsy is not necessary in a patient with high suspicion of light chain cast nephropathy (LCCN), namely AKI with high serum free light chains and predominant light chain proteinuria. However, we know that biopsy confirmation might be helpful when confounding conditions are present (diabetes, albuminuria). Additionally, histology might detect coexisting ‘monoclonal’ nephropathies such as light chain deposition disease or amyloidosis. But is there additional value?
Virginie Royal and coworkers just published on the histology of light chain cast nephropathy and its ability to predict renal and patient outcomes in a retrospective multicenter cohort of 178 patients. Medullary inflammation, giant cell reaction around casts and a high number of casts correlated with lower baseline GFR. The mean number of casts/mm² and the degree of IFTA were independently associated with eGFR during follow-up. As the extent of cast formation did not correlate with FLC in serum, it is possible that the renal biopsy is a more direct read-out of the capacity of a certain light chain clone to have affinity for Tamm-Horsfall protein and to exert renal damage than serum concentrations of the clone. 
Additionally, renal response to treatment was (in addition to hematologic response) in this study significantly associated with a greater overall survival compared to no renal response.