Human herpesvirus 8+ polyclonal IgMλ B-cell lymphocytosis mimicking plasmablastic leukemia/lymphoma in HIV-infected patients.

PurposeMulticentric Castleman disease (MCD) is a distinct lymphoproliferative disorder characterized by inflammatory symptoms, lymphadenopathy, splenomegaly, and cytopenia. Kaposi's sarcoma-associated herpesvirus (KSHV), also called human herpesvirus-8 (HHV-8), is the cause of virtually all cases of MCD occurring in patients with HIV infection. MCD lesions characteristically contain HHV-8-infected polyclonal IgM plasmablasts. A high frequency of HHV-8-related non-Hodgkin lymphoma has been reported in these patients. Patients and methodsWe now report on three patients who presented with severe symptoms of MCD, extreme splenomegaly, and rapid expansion of B-cell lymphocytosis (44-81%) attributable to circulating HHV-8 positive plasmablasts. ResultsThe circulating plasmablastic cells shared the phenotype (IgM, CD19+, CD20- CD138-) of HHV-8-infected cells from MCD lesions, mimicking the leukemic phase of large B-cell lymphoma occurring in HHV-8-related MCD. These patients displayed a very high HHV-8 viral load in blood (>7 logs HHV-8 DNA copies/ml) and high levels of serum vIL-6, the viral homolog of human interleukin 6. Serum IL-6 and IL-10 were also abnormally elevated. HHV-8-infected cells were demonstrated by immunoglobulin gene rearrangement analysis, to be polyclonal and likely represent an expansion of HHV-8-infected cells similar to those found in MCD lesions. ConclusionThus, the spectrum of HHV-8-related plasmablastic lymphoproliferative disorders in patients with HIV infection is expanded to include HHV-8+ polyclonal IgM B-cell lymphocytosis. At onset, this lymphoproliferative disorder may mimic plasmablastic leukemia/lymphoma. Recognizing this unusual complication may have important implications in treatment decision avoiding unnecessary toxicity to the patients.