ARF is a disease that has a specific etiologic agent yet has some similarities to the rheumatoid-collagen-vascular group. The etiologic agent is the beta-hemolytic Lancefield group A Streptococcus. Apparent hypersensitivity or other effect of this organism causes connective tissue changes manifested by focal necrosis of collagen and the development of peculiar aggregates of histiocytes called […]