After just seven months of scientific investigations, researchers have identified several key features of the syndrome in which people have markedly low levels of the white blood cell CD4+ T lymphocyte, yet no signs of infection with the HIV or related viruses.
In an editorial in the Feb. 11 issue of "The New England Journal of Medicine," Anthony S. Fauci, M.D., director of the National Institute of Allergy and Diseases (NIAID), reviews four reports and a letter published in the same issue that focus on the syndrome, known as idiopathic CD4+ T lymphocytopenia (ICL).
We can reasonably conclude that ICL is a rare syndrome, is not new and is not caused by HIV-1 or -2 or human T lymphotropic virus (HTLV)-I or -II nor by a transmissible agent," says Dr. Fauci. "Furthermore, the syndrome is heterogenous in that it affects a demographically diverse population and has different clinical manifestations, both of which make it dissimilar from HIV infection and AIDS."
ICL first came to the public eye during the IXth International Conference on AIDS in Amsterdam in July 1992. On Aug. 14, 1992, the U.S. Centers for Disease Control and Prevention (CDC) hosted a meeting at which more than 270 scientists exchanged information.
Cases of ICL have been identified since 1983, Dr. Fauci notes, and it is likely that others would have been identified much earlier. However, routine determination of CD4+ T cell counts has been practiced only since the early to mid-1980s in association with the HIV epidemic. The cells are the primary target of HIV.
Cases of opportunistic infections without known causes of suppressed immune systems, he adds, have been reported for decades, and some of these almost certainly would have fit the current definition of ICL.
Patients have ICL if they have two or more counts of CD4+ T cells below 300 cubic millimeters of blood or a percentage of such cells that is less than 20 percent of the total number of lymphocytes, no evidence of HIV-1 or -2 infection and no defined cause or therapy that accounts for the low level of CD4+ T cells.
On July 30, 1992, NIAID announced that it would make its network of research resources immediately available for clinical and laboratory investigations of ICL. That same day, NIAID notified its sites for clinical trials on AIDS, collaborating clinicians, grantees and contractors about the investigation. Both the National Institutes of Health and CDC encouraged physicians to review their files to identify any patients that met the disease criteria.
As of Dec. 17, 1992, NIAID had received inquiries about 119 patients. Specimens from five of these patients have been sent to CDC, and 46 patients did not meet ICL criteria. More information was gathered on 67 patients, 20 of whom came to NIAID and were evaluated. One patient has been lost to follow-up.
In summarizing the NEJM reports, Dr. Fauci says "it is highly likely that there is not a common cause for ICL. Nonetheless, there may be certain common causes among different subgroups of patients that are yet unrecognized. In fact, the identification of these patients and the discovery of ICL may present a unique opportunity to solve certain of the mysteries associated with "idiopathic" immunosuppressed states."
Prepared by: Office of Communications National Institute of Allergy and Infectious Diseases National Institutes of Health Bethesda, Maryland 20892 (301) 496-5717