Analysis of the Epstein-Barr viral genome in so-called malignant histiocytosis syndrome.

Malignant histiocytosis has been described as a proliferation of morphologically atypical histiocytes, but it is difficult to determine whether or not malignant proliferation is present based on morphology alone. Recently the disorder has been thought to be heterogeneous, and therefore a true histiocytic origin is considered to be rare. The Epstein-Barr virus (EBV) is thought to have the ability to transform human cells. Therefore, eight cases of malignant histiocytic (MH) syndrome and five cases of virus-associated hemophagocytic syndrome (VAHS) were analyzed using a polymerase chain reaction (PCR) and the in situ hybridization (ISH) method in order to determine their relationship to EBV infection. At the same time, the cellular origin of these syndromes was also studied. The results indicated that three of the MH cases were derived from T cells while four the MH cases were from histiocytes. The amplification of the EBV-LYDMA region, which was used to determine the monoclonality, was detected in two MH cases and one VAHS case, and all these cases showed only one band. An ISH study also demonstrated the presence of an EBV in these three cases. One of the EBV-positive cases revealed an amplification of the EBV-LYDMA region by the PCR method before showing any sign of MH clinically. In the VAHS cases, the EBV genome was detected in hemophagocytic cells. The EBV-positive cases all demonstrated a rapid clinical course. Based on these results it is possible that EBV infection causes similar rapid clinical features in some cases of both MH and VAHS by the same mechanism.