[Case of infectious mononucleosis with suspected primary coinfection with Chlamydophila (Chlamydia) pneumoniae and Epstein-Barr virus].

A 26-year-old male was hospitalized with fever and pharyngeal pain. Liver dysfunction and an increase in the percentage of atypical lymphocytes in the peripheral blood were detected. Computed tomography showed pneumonia involving the right lung and synpneumonic pleural effusion. Serum immunological tests showed positive results for Epstein-Barr virus (EBV) viral capsid antigen (VCA) IgM and IgG antibodies and Chlamydophila (Chlamydia) pneumoniae (C. pneumoniae) IgM and IgA antibodies on admission. The pneumonia and pleural effusion were no longer detectable after a week of treatment with starting azithromycin. At 7 weeks after admission, the liver function test results returned to within normal limits, the serum became negative for EBV VCA IgM antibody, the C. pneumoniae IgM antibody titer decreased, and the C. pneumoniae IgA and IgG antibody titers increased. This case was suspected to have infectious mononucleosis caused by primary coinfection with C. pneumoniae and EBV.