A complicated evaluation of the response to the therapy in a patient with light chain deposition disease

Light chain deposition disease (LCDD) is characterized by tissue deposition, mostly in the kidney, of monoclonal immunoglobulin light chains (LCs), causing renal dysfunction and end-stage renal disease. The main goal of therapy is the reduction of LCs concentration, that can be obtained using chemotherapy approaches. We report the case of a 28-year-old man with LCDD (IgGκ type) and underlying multiple myeloma who, after three ineffective lines of therapy, started a treatment with daratumumab, a monoclonal antibody (mAb, IgG1κ type) drug, recently introduced for multiple myeloma treatment. The drug seemed effective but a IgGκ spike remained visible at standard immunofixation. To discriminate the drug from the patient monoclonal component, immunofixation with Hydrashift system was used. This tool identified the visible IgGκ as mAb drug and complete response was documented. This case showed the utility of new clinical assays for the evaluation of response to therapy in patients treated with mAb drugs.