Clinically, in young immunocompetent adults, Epstein-Barr virus (EBV) usually manifests as infectious mononucleosis (IM). Typical clinical findings of EBV IM include fever, profound fatigue, pharyngitis, bilateral posterior cervical adenopathy, and splenomegaly. Respiratory involvement with EBV IM may occur, but is distinctly rare. We present a case of a 20 year old female who with classic EBV IM, but was inexplicably dyspneic and hypoxemic. Further diagnostic testing confirmed co-infection with Mycoplasma pneumoniae. As a non-zoonotic atypical community-acquired pneumonia (CAP), M. pneumoniae may rarely be accompanied by severe hypoxemia and even acute respiratory distress syndrome. She represented a diagnostic dilemma regarding the cause of her hypoxemia, i.e., due to EBV IM with pulmonary involvement or severe M. pneumoniae CAP. The patient slowly recovered with respiratory quinolone therapy.
Keywords: atypical lymphocytosis; atypical pneumonia; bacterial and viral co-infection; cold agglutinins; community-acquired pneumonia; elevated serum transaminases; non-exudative pharyngitis.