During this period, vasculitis emerged as an immune-mediated, multi-system process with evidence for immune complex deposition driving vessel inflammation. Research increasingly classified vasculitis by vessel size and organ involvement, integrating histology, immunofluorescence, and early imaging to illuminate pathogenesis. Pediatric forms such as Henoch-Schönlein purpura and the newly described Kawasaki disease highlighted the long-term cardiovascular and systemic risks, shaping a prognosis-driven approach to treatment.