In infectious mononucleosis, the pharyngitis is also exudative, but splenomegaly and generalized adenopathy are typical, and laboratory findings are often diagnostic (atypical lymphocytes, elevated liver enzymes, and a positive heterophil or other serologic test for mononucleosis). Uncomplicated streptococcal pharyngitis improves within 24-28 hours if penicillin is given and by 72-96 hours without antimicrobials.