Posttransplantation plasmacytic proliferations related to Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV), which was originally detect ed in Kaposi's sarcoma, also has been found in primary effusion lymphomas ( PELs) and some cases of multicentric Castleman's disease. We describe two t ransplant recipients who developed Kaposi's sarcoma and a spectrum of nonne oplastic lymphoproliferative disorders that show pronounced plasmacytic and plasmacytoid features. The first patient had recurrent pleural effusions a nd Castleman's disease-like changes in lymph nodes. The second patient had systemic lymphadenopathy and hepatosplenomegaly secondary to diffuse infilt ration by polyclonal plasma cells and plasmacytoid B lymphocytes that clini cally mimicked Epstein-Barr virus (EBV)-associated posttransplant lymphopro liferative disease. In both cases, KSHV DNA was detected by polymerase chai n reaction and Southern blotting, and KSHV vIL-6 protein expression was ide ntified in affected tissues by immunohistochemical localization. In contras t, no evidence of KSHV coinfection was detected in any of 31 EBV-related po sttransplant lymphoproliferative disorders or 112 non-PEL lymphomas tested. The pathologic findings in these two patients were not representative of m alignancy by morphologic, immunophenotypic, or molecular criteria. This stu dy underscores the marked propensity for hematolymphoid proliferations asso ciated with KSHV infections to show plasmacytic features. Additionally, thi s study describes use of an antibody reactive against KSHV vIL-6 that can r eadily detect a subpopulation of KSHV-infected hematopoietic cells.