Transplantation

Infection with human herpesvirus 8 (HHV-8) has been consistently associated with the development of Kaposi sarcoma (KS) and rare lymphoproliferative disorders (^1,2). HHV-8 is not ubiquitous in the general population. Seroprevalence rates are low in the United Kingdom and United States and are higher only in certain geographic areas (e.g., the Mediterranean and Africa) with a known high incidence of classic or endemic KS (^1,2). In the setting of transplantation, KS is observed mainly in kidney and liver allograft recipients and is caused by either reactivation of a preexisting HHV-8 infection in the recipient or a primary infection with the virus transmitted from the donor (^3,4). Only two cases of primary effusion lymphoma (PEL), one case of Castleman disease, two cases of polyclonal plasmacytic proliferations, and one case of monoclonal lymphoproliferative disease of polymorphic type have so far been described in recipients of solid organs, after HHV-8 infection (⁴). The occurrence of nonneoplastic complications associated with HHV-8 primary infection or reactivation has been also reported, although rarely, in transplant patients (^4–6). We report the occurrence of severe pancytopenia with normocellular or hypercellular bone marrow (BM) with hemophagocytosis after HHV-8 primary infection in a renal transplant patient, which has been successfully treated with foscarnet.

CASE REPORT

A 61-year-old Italian man, seronegative for HHV-8 infection, developed visceral KS in April 1999, 4 months after receiving a renal allograft from an HHV-8 seropositive cadaver donor. Further clinical details and the serologic and molecular studies showing seroconversion and high levels of viremia, indicative of a recent primary infection with HHV-8 in this patient, have been reported elsewhere (⁶). Thirty days after the diagnosis of KS, the patient revealed progressive peripheral cytopenia. The white cell count declined to 1600/mm³, the platelet count to 8000/mm³, and the hemoglobin level to 6.7 g/dL (Fig. 1). No signs of disseminated intravascular coagulation or hemolysis were detected. A computed tomographic scan of the chest and abdomen revealed neither lymph node nor spleen enlargement. A core biopsy of BM revealed normocellular or hypercellular BM, with signs of hemophagocytosis (Fig. 2). Moderate plasmacytosis was also present. There was neither KS nor lymphomatous infiltration of the bone marrow. No evidence of herpesviruses (types 1 and 2, varicella-zoster virus, Epstein-Barr virus [EBV], HHV-6, HHV-7, and cytomegalovirus) and parvovirus B19 was detected either in the serum or in the BM, by described polymerase chain reaction (PCR) protocols (⁶). Cytomegalovirus antigenemia was repeatedly negative. Cyclosporine was stopped, and methylprednisolone was reduced. Administration of intravenous immune globulin (total dose, 175 g) was ineffective, and the patient received platelet and red blood cell transfusions. Treatment with foscarnet (80 mg/kg twice daily) for 2 weeks led to a rapid increase and normalization of blood cell counts (Fig. 1). After antiviral therapy, the patient was treated with a course of microsomal daunorubicin every fortnight, for a total of five courses, at the end of which KS lesions completely regressed. Immunosuppressive regimen was then gradually restored, and the patient is still in complete remission, with normal blood counts, about 20 months later.

HHV-8 DNA was measured on the serum and BM samples by PCR with primers specific for two different viral genes, orf 26 and K1, as previously described (⁶). The nested PCR for the K1 gene detected as few as 50 HHV-8 copies, as determined by serial dilutions of the HHV-8-positive BCBL-1 cell line (⁶). To measure the amount of viral DNA present in serum, a semiquantitative method was used, with 10 μl of serum, equivalent to the amount of extracted DNA, used in the PCR assay (⁶). PCR products were also subjected to direct automated sequence analysis. Furthermore, immunohistochemical analysis with a polyclonal rabbit antibody against the HHV-8 latency-associated nuclear antigen (LANA) 1 was performed at a dilution of 1:500 in phosphate-buffered saline in the BM biopsy specimen as well as in a PEL cell line (BCBL-1), according to an alkaline-phosphatase–anti-alkaline phosphatase technique (⁶).

HHV-8 DNA (50,000–100,000 copies) was detected by PCR in the cell-free serum sample obtained from the patient concomitantly with the peripheral cytopenia (Fig. 1). On the basis of the sequencing of the K1 gene, the HHV-8 variant in this patient was classified as clade C (⁶). Then, during and immediately after treatment with foscarnet, the viral load progressively decreased and HHV-8 DNA was no longer detectable in the first available cell-free serum collected 38 days after initiation of antiviral treatment, concomitantly with normal blood cell counts (Fig. 1). PCR negativity for HHV-8 DNA persisted for almost 2 years without recurrence of cytopenia. HHV-8 LANA was expressed in the nuclei of approximately 1–2% of the bone marrow cells. Cells expressing LANA appeared morphologically to be immature BM cells (Fig. 3). LANA was present in distinct subnuclear domains (Fig. 3) in a pattern similar to that seen in cultured PEL cell lines (not shown) (⁶).

DISCUSSION

We recently described an acute syndrome of fever, splenomegaly, and cytopenia caused by BM aplasia after HHV-8 primary infection in a renal transplant patient (⁶). We also documented the association between HHV-8 reactivation and the occurrence of fever and cytopenia because of BM failure with plasmacytosis in a HHV-8 seropositive autologous peripheral blood stem cell transplant patient (⁶). Expression of HHV-8 LANA within immature BM cells strengthened the causal relation between HHV-8 infection and the BM failure in both patients (⁶).

The clinical course of our patient in the present study shows that after primary infection, HHV-8 may also establish a latent infection of BM, documented by the expression of HHV-8 LANA within the BM cells, without exerting a myelosuppressive effect. However, peripheral cytopenia, which is likely to be immune mediated, may result from HHV-8 primary infection. Consistent with this, early morphologic studies have reported that peripheral blood cytopenia in one or more cell lineages, in the presence of a normocellular or hypercellular BM, was a common finding in homosexual men with KS, with or without AIDS (^7,8). The behavior of HHV-8 resembles that of another gamma-herpesvirus, the EBV. Aplastic anemia rarely complicates infection with EBV, but, rather frequently, pancytopenia with normocellular or hypercellular BM may accompany or follow EBV-associated infectious mononucleosis (⁸). In transplant patients, also infection with a beta-herpesvirus, the cytomegalovirus, may be associated with hematologic abnormalities, including leukopenia, thrombocytopenia, and atypical lymphocytosis (⁸). Hemophagocytosis is often associated with infections, and two cases of hemophagocytic syndrome, responsive to ganciclovir and foscarnet, have been previously described in two HIV-positive subjects with KS (^9,10).

CONCLUSION

HHV-8 infection should be considered in the differential diagnosis of possible causes of peripheral cytopenia in transplant patients with KS or in patients originating from endemic areas for HHV-8 infection. The prompt response to antiviral therapy in our patient suggests that foscarnet may be a useful therapeutic option in the management of HHV-8-associated cytopenia in the transplantation setting.

Acknowledgment.

The authors thank Professor Thomas F. Schulz, Institut für Virologie, Hannover, Germany, for providing the polyclonal antibody against LANA.

REFERENCES