A case of pure red cell aplasia complicated with diffuse large B cell lymphoma, T-cell-rich/histiocyte-rich variant: effectiveness of rituximab and implications for a common immunopathogenic role of B lymphocytes. 
Diffuse large B cell lymphoma, T-cell-rich/histiocyte-rich variant (DLBL-TH), is characterized by the presence of neoplastic B cells set in a background containing numerous non-neoplastic T lymphocytes and histiocytes.  We report here the case of a patient with DLBL-TH who developed overt pure red cell aplasia (PRCA) following chemotherapy and autologous peripheral blood stem cell transplantation.  Posttransplantation bone marrow biopsies revealed the absence of erythroid precursors associated with lymphoid aggregates composed of B cells mixed with numerous T cells and histiocytes.  Administration of rituximab has led to complete recovery of erythropoiesis, which was associated not only with B cell depletion but also with a marked reduction in bone marrow T cells and histiocytes.  These observations strongly suggest the particular pathogenetic role of the patient's B cells in inducing PRCA and recruiting T cells and histiocytes in situ.