Selected aspects of acute and chronic infectious mononucleosis and mononucleosis-like illnesses for the practicing allergist.

The diagnosis of EBV-IM or a heterophil-negative mononucleosis-like syndrome is best approached by combining morphologic and serologic data. The minimal hematologic criteria should always be searched for before accepting a case as IM or an IM-like illness. If minimal morphologic data are not rigidly adhered to, the number of heterophil-negative cases included under the umbrella of IM or an IM-like illness will swell and include a variety of other illnesses where early diagnosis may be important for treatment purposes. When EBV studies are indicated, the entire profile (VCA-IgM, VCA-IgG, and anti-EBNA) should be performed. Anti-VCA-IgG titers alone, for example, are of very limited usefulness unless they are negative (less than 1:10), in which case the diagnosis of EBV-IM is excluded. The main problems connected with the diagnosis of the CMS center about the nonspecificity of both clinical and EBV serologic data. Thus, a significant effort must be made to rule out underlying disease, especially those chronic illnesses with immunosuppressive effects that are capable of reactivating the EBV latency state and producing EBV serology similar to that seen in CMS. Other dilemmas relate to diagnostic cut-off levels for particular EBV-related tests, including antibodies to EA and the relative unavailability of several tests for detection of subtle immunodeficiency or T-cell dysfunction in individual patients with suspected CMS. Future efforts will be directed to the diagnostic usefulness of antibody responses to well-defined recombinant fragments of the EBV genome (ie, anti-EBNA1 vs. -EBNA2 titers).