Concomitant EBV-related B-cell proliferation and juvenile myelomonocytic leukemia in a 2-year-old child.

We present a case of a 2-year-old girl, who developed concomitant EBV-related B-cell proliferation and juvenile myelomonocytic leukemia (JMML). JMML was initially not recognized because of predominant B-cell proliferation. The activating N-RAS mutation was retrospectively already detectable at this early stage. Our findings support the hypothesis that EBV may contribute to JMML pathogenesis by stimulating pre-existing malignant clones. However, such stimulation of leukemic clone does not require the direct incorporation of the virus into myeloid progenitors. Most probably a cytokine burst resulting from EBV infection allows expansion of pre-existing malignant myeloid progenitors. Further studies are required to delineate exact mechanisms of EBV-related promotion of the JMML clone.