University of Arizona-South campus Tucson, Arizona, United States
Abstract Text: Lymphoplasmacytic lymphoma (LPL) causes 3% of amyloidosis cases, primarily amyloidosis with light chains (AL). Amyloidosis with heavy chains (AH/AHL) is an uncommon form of immunoglobulin-derived amyloidosis with the μ heavy chain variant known to be the rarest type. The anti-CD38 monoclonal antibody, Daratumumab has recently propelled itself in the forefront of treatment of AL amyloidosis after the publication of the Andromeda study.
We present a case of an elderly male with a history of IgM κ lymphoplasmacytic lymphoma who underwent a renal biopsy revealing the presence of μ heavy and λ light chains. His bone marrow biopsy demonstrated κ light chain restriction by flow cytometry accompanied by amyloid deposition. The patient’s serum had elevated free κ and λ light chains with a free light chain (FLC) ratio of 3.17. Serum immunofixation was positive for IgM κ and λ light chain clones. He completed 6 cycles of Cyclophosphamide, Bortezomib, Dexamethasone, and Rituximab (CyBorD+R) resulting in the normalization of the FLC ratio, but he continued to present with persistently elevated M protein and IgM κ and λ light chains on immunofixation. Thereafter, Daratumumab was initiated which led to a negative immunofixation study after 2 cycles of the monoclonal antibody accompanied with reduction in the excretion of protein in the urine.
The patient achieved a complete hematological response with daratumumab. To date, our case is the only reported μ heavy and λ light chain amyloidosis patient with bi-clonal (IgM κ and λ) gammopathy to be successfully treated with daratumumab.
