Which finding would be sufficient to make an initial diagnosis of acute rheumatic fever in a patient with recent streptococcal infection?

• A. Carditis
• B. Erythema marginatum
• C. Chorea and reversible prolonged PR interval
• D. Polyarthralgia and elevated ESR

Answer: (C)

The key idea is recognizing how acute rheumatic fever is diagnosed when there’s a recent streptococcal infection. Sydenham chorea is one of the major Jones criteria and is highly specific for ARF. When someone develops chorea after a strep infection, it strongly points to ARF even if other classic signs aren’t present yet. The reversible prolongation of the PR interval indicates transient cardiac conduction involvement, which supports the diagnosis of inflammatory heart involvement (carditis) that can accompany ARF.

So, chorea in the setting of a recent streptococcal infection provides a robust basis for an initial ARF diagnosis, because chorea is a major manifestation and the infection history satisfies the necessary antecedent criterion. In practice, other combinations of findings can also establish ARF, but this particular pairing is especially compelling and often sufficient to begin treatment to prevent rheumatic heart disease.