Clinical and molecular characteristics of patients with non-amyloid light chain deposition disorders, and outcome following treatment with high-dose melphalan and autologous stem cell transplantation

Light chain deposition disease (LCDD) is caused by a clonal plasma cell disorder in which fragments of monoclonal immunoglobulin light chains form non-fibrillary deposits in various tissues resulting in organ dysfunction. Crystal storing histiocytosis (CSH) is another light chain deposition disorder in which monoclonal light chains form intracytoplasmic crystals. Both are uncommon diseases for which there is limited treatment experience. Between 2003 and 2005, five patients with LCDD and one with CSH were treated at Boston University Medical Center with high-dose melphalan and autologous peripheral blood stem cell transplantation (HDM/SCT). Five of the six patients had predominantly renal involvement, and one patient with LCDD had biopsy-proven deposits in the myocardium. Molecular characterization revealed that the pathologic light chains were kappa in four of the six patients, and sequence analysis revealed unusual germline donor genes and high rates of amino-acid substitutions. One light chain sequence encoded a new potential N-linked glycosylation site, and another showed evidence of antigen selection. All patients are alive and five of the six patients are in complete hematologic remission at a median follow-up of 12 months (range 4-29 months) after HDM/SCT. In our experience, HDM/SCT is a feasible and effective treatment approach for these disorders.