Which skin rash is pathognomonic of rheumatic fever?

• A. Erythema marginatum
• B. Erythema nodosum
• C. Diffuse petechiae
• D. Purulent bullae

Answer: (A)

Erythema marginatum is the rash most closely associated with rheumatic fever. It appears as a ring-shaped, nonpruritic eruption with a pale center, often on the trunk and proximal limbs, and it tends to come and go. Its appearance is highly specific for rheumatic fever and is one of the major Jones criteria used to support the diagnosis. Other skin findings listed—erythema nodosum (tender nodules on the shins), diffuse petechiae (tiny red spots from bleeding), and purulent bullae (blistering infections)—do not have the same diagnostic specificity for rheumatic fever, so they don’t serve as the definitive clue that erythema marginatum provides.