Infection with Arcanobacterium haemolyticum, a gram-positive rod, causes pharyngitis, typically in adolescents and young adults.

One report that analyzed 3992 throat cultures for A. haemolyticum and beta-hemolytic streptococci found that 0.5% of throat cultures were positive for A. haemolyticum, and most patients with positive cultures with this organism were between 15 and 25 years old. Another study of army conscripts with sore throat identified A. haemolyticum in 1.4% of throat cultures (asymptomatic carriage was noted in 0.4% of control subjects).

Patients present with exudative pharyngitis, cervical lymphadenopathy, and fever. Clinically, this presentation can be similar to pharyngitis due to group A streptococcus.

Patients with A. haemolyticum infection may also develop a rash that appears similar to the rash caused by scarlet fever (although other rashes, including maculopapular rashes, have been described). The rash, if present, is usually seen first on the extensor surfaces of the extremities, sparing the palms.

Patients with A. haemolyticum infection will usually not have symptoms that are more commonly associated with viral infections, including cough and conjunctivitis.

Very rarely, this organism may cause serious infections, including endocarditis and bacteremia.