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You saw a 17-year-old boy with 4 days of fever and sore throat. Exam revealed an erythematous pharynx with exudate but no vesicles or ulcers, tender bilateral anterior cervical lymph nodes, and a sandpaper-like pruritic rash. The rash started the day before on the distal extremities first, spreading to the torso and face. He has had no cough, rhinorrhea, nor conjunctivitis. The patient had been seen on day #2 of illness and had a negative rapid strep test. At that time he was told he had viral pharyngitis. You repeated the rapid strep, which was still negative, and sent a throat culture. You started him on cephalexin and on a follow-up phone call the next day he is improving.
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December 16, 2025 at 6:43 pm
Arcanobacterium haemolytica is a new entity for me. I retired from medicine in 2018 (emergency medicine and pediatric residencies). Only when my grandson developed a sore throat and went to urgent care in Canada did I hear of testing for this bacteria as well as strep. I’d like more info on it.
December 18, 2025 at 12:47 pm
I also had not heard much about it until I listened to a recent Peds ID lecture. I’ve posted the answer with more info
December 18, 2025 at 12:45 pm
E) Arcanobacterium haemolyticum
The patient has symptoms commonly seen with strep pharyngitis: fever, pharyngeal exudate, sandpaper rash (scarlet fever), and lack of viral cough and cold symptoms, but he tested negative for strep. Answers A and B are not supported due to the lack of viral cough and cold symptoms (A) and pharyngeal vesicles (B). Group B strep is not associated with exudative pharyngitis in teens. Fusobacterium necrophorum is a common cause of Lemierre’s syndrome, which is a rare disease. In Lemierre’s, an oropharyngeal infection spreads infected emboli causing jugular vein thrombophlebitis and sepsis. Arcanobacterium haeomlyticum can cause symptoms similar to Group A strep pharyngitis, including a sandpaper rash. It may be missed on throat culture if the lab does not explicitly look for it. It often responds to penicillins, cephalosporins, and macrolides.
December 22, 2025 at 6:23 pm
Thank you, that was a great description