Recurrence of monoclonal gammopathy associated with donor-derived myelodysplastic syndrome after cord blood stem cell transplantation.

Myelodysplastic syndrome (MDS) is known to be associated with functional abnormalities of B cells, including hypergammaglobulinemia and monoclonal gammopathy (MG). However, the pathogenesis of these immunological disorders has not been clarified. We report a patient who developed donor-derived MDS followed by leukemic transformation after cord blood transplantation for MDS with MG. Interestingly, MG reappeared before development of donor-derived MDS. We analyzed the immunoglobulin allotype gene polymorphisms to determine whether the MG after cord blood transplantation was of recipient origin or donor origin. Results of genetic analysis and enzyme-linked immunosorbent assay of IgG1 allotype revealed that the MG after cord blood transplantation was of donor origin. Although the mechanism of donor-derived MG remains unclear, the persistent presence of recipient's antigen presenting cells might have induced the abnormal immunoglobulin production.