Blood, 15 July 2001, Vol. 98, No. 2, pp. 255-255
A severe illness associated with EBV infection of T and NK
cells
There has been much uncertainty regarding the identity of
chronic active EBV infection and where it fits into the spectrum of
EBV-associated disorders. Clinical observations and laboratory studies
had defined it on the basis of 3 features: severe illness that begins
as a primary EBV infection or that is associated with abnormal EBV
antibody titers; histologic evidence of organ disease, such as
hepatitis, pneumonitis, or bone marrow hypoplasia; and demonstration of
EBV antigens or EBV DNA in tissue. Now, Kimura and colleagues (page
280) add to our understanding of chronic active EBV infection by
extensively evaluating 30 patients with the above features. Based on
their data as well as on earlier smaller studies, they conclude that
chronic active EBV infection is an illness characterized by EBV
infection of T cells or NK cells. The disease may be distinguished into
2 subgroups based on the cell type infected, each group with somewhat
different clinical manifestations and outcomes. Patients with the
T-cell type had a shorter survival time than patients with the NK-cell type.
EBV usually infects B cells and, perhaps, epithelial cells, but not T
cells or NK cells. Yet in patients with chronic active EBV infection, T
or NK cells were the blood cells predominantly infected by the virus.
These cells had probably undergone clonal expansion because virus
recovered from the blood was generally monoclonal and blood cells often
displayed various chromosomal aberrations. Thus, chronic active EBV
infection might best be considered to be a lymphoproliferative disease.
Indeed, many patients go on to develop EBV-positive lymphomas of T or
NK phenotype. The question is why EBV infects these unusual cell
targets. Here the authors provide some important negative information:
the SAP/SH2D1A gene that is mutated in X-linked
lymphoproliferative disease, an inherited disease resulting in
unregulated growth of EBV-infected B cells, was not affected in these
patients. The search for a genetic defect underlying chronic active EBV
infection will certainly continue.
Giovanna Tosato
National Cancer Institute
