Erythema Marginatum

A 9-year-old boy from rural India presents 3 weeks after culture-confirmed group A streptococcal pharyngitis with migratory polyarthritis of the knees and ankles, and a new pansystolic apical murmur. On examination, you note the characteristic rash marked **A** on his trunk and proximal limbs: pink-red annular lesions with central clearing and sharply demarcated raised margins that wax and wane within hours, blanch on pressure, and spare the face. ASO titer is 850 (elevated), and ECG shows prolonged PR interval. Which of the following best describes the clinical significance of the rash marked **A** in this patient's diagnosis?