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- Acute rheumatic fever (ARF) is an autoimmune, inflammatory response to pharyngeal infection with group A Streptococcus (GAS) that affects multiple organ systems.
- Can lead to rheumatic heart disease (RHD) if not treated in the acute phase
- Largely, a disease of poverty and has disappeared from many affluent parts of the world
- Recurrence in adults and children is common without adequate antibiotic treatment.
- Organ systems affected include cardiovascular, nervous, hematologic, immunologic, lymphatic, skin/exocrine, and musculoskeletal.
Most cases occur in children ages 5 to 15 years; rare in children <5 years (1)
- ARF and RHD are largely restricted to low-income countries and marginalized sections of society in wealthy countries.
- Male = female, but females more likely to develop chorea and RHD.
- Endemic regions include South Pacific, indigenous populations of Australia and New Zealand, Africa, Asia.
- Worldwide, incidence has been declining for 25 years, attributed to increasing antibiotic use and improved living conditions. The large majority of new cases are in developing countries.
- Mean worldwide incidence ranges from 8 to 51/100,000 school-aged children (1); 500,000 new cases of ARF occur annually (2).
- Incidence of ARF in the United States is currently <2/100,000 school-aged children.
- It is estimated that up to 3% episodes of untreated acute GAS pharyngitis go on to develop ARF (1).
- In developing areas of the world, RHD is estimated to affect >33 million people and is the leading cause of cardiovascular death during the first 5 decades of life.
- Prevalence has been rising due to improved medical care and longer survival (despite decreasing incidence of ARF).
Etiology and Pathophysiology
- ARF is preceded 2 to 3 weeks by GAS (Streptococcus pyogenes) tonsillopharyngitis, a gram-positive bacterial infection.
- Pathogenic mechanism is not completely understood.
- Molecular mimicry plays an important role: The GAS M protein and the carbohydrate antigen (N-acetyl-β-D-glucosamine) share antigenic epitopes with human cardiac tissue and neuronal cells in the basal ganglia (1). These antigens cross-react with cardiac and vessel endothelial proteins, leading to an inflammatory cascade.
- Joint involvement is a likely result of immune complex accumulation.
- Susceptibility is associated with certain genetic polymorphisms of genes involved in the innate and adaptive immune pathways; not fully understood
- ARF appears to be a heritable and susceptibility is most likely polygenic with variable and incomplete penetrance.
- Increased susceptibility in certain populations, including indigenous Australians, New Zealand Maori, and Pacific Islanders
- Poverty, household crowding, and social disadvantage are the strongest risk factors.
- Genetic susceptibility and ethnic predisposition possibly increase risk.
- Primary prevention: Antibiotics are effective at reducing incidence of ARF after known or suspected GAS pharyngitis. Number needed to treat is 100 (3). Appropriate treatment of streptococcal pharyngitis prevents ARF in most cases.
- Secondary prevention: long-term antibiotic prophylaxis (up to 5 to 10 years) to prevent recurrence, which can lead to RHD.