<prompt> What is the diagnosis in this patient who appeared sick, had a bull neck, and was tachycardic?DiphtheriaEpiglottitisInfectious mononucleosisRheumatic fever  <response>: Answer A. DiphtheriaThe patients features are typical of diphtheria. Her throat culture was positive for Corynebacterium diphtheriae. The patient recovered after the initiation of treatment with penicillin. 