A 75-year-old woman presented with altered mental status, septic picture, and 
influenza-like symptoms. Initial investigations revealed atypical lymphocytosis, 
thrombocytopenia, elevated liver enzymes, and a positive monospot test result. 
Further investigation showed the Epstein-Barr virus viral capsid antibody 
IgM/IgG and Epstein-Barr virus DNA by polymerase chain reaction to be negative; 
however, interestingly her cytomegalovirus (CMV) IgM and IgG were positive, 
suggesting that her mononucleosis-like syndrome was due to acute CMV infection. 
Herein, we report the first case of a heterophile-positive mononucleosis 
syndrome caused by acute CMV infection in an elderly immunocompetent woman. This 
case conveys that monospot test can yield false-positive result in the setting 
of acute CMV infection.