Rheumatic fever, which is typically referred to as acute rheumatic fever, represents a delayed and non-suppurative consequence of a pharyngeal infection with the group A streptococcus. Group A streptococcus contains a myriad of cell surface components, many of which are molecularly similar to human tissues such as heart valve tissue, which can subsequently induce a harmful immune response.
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Following a latent period of two to three weeks after the initial pharyngitis, the first signs or symptoms of rheumatic fever can slowly emerge. The disease usually has an onset in childhood and presents with various manifestations that include carditis, arthritis, chorea, subcutaneous nodules, and erythema marginatum.
Epidemiology of the disease
In developing areas of the world, rheumatic fever and subsequent heart disease affect approximately 20 million people, thus representing the leading causes of cardiovascular death during the initial five decades of life. Although the disease most commonly occurs in children between the ages of 5 and 15, it can affect individuals of relatively any age.
Reliable data on the incidence of rheumatic fever are scarce. Still, it is estimated that globally there are an estimated 470,000 new cases of rheumatic fever and 233,000 deaths each year that are attributable to this condition. The mean incidence of acute rheumatic fever is 19 for every 100,000 individuals, with most of the cases occurring in developing countries and among indigenous groups.
In developed nations, there is a much lower incidence of rheumatic fever that is estimated at 2 to 14 cases for every100,000 people. This reduced risk of rheumatic fever is likely due to good hygienic practices and the routine use of antibiotics for acute pharyngitis. It is also well established that both environmental and socioeconomic factors play indirect, but essential roles in the magnitude and severity of this condition.
During epidemics of the disease in the mid-1900s, as many as 3% of untreated acute streptococcal sore throats were followed by rheumatic fever, whereas in endemic infections, the incidence of rheumatic fever can be substantially less. Shortage of resources for providing quality health care, inadequate expertise, and a low level of awareness of the disease in the community can influence the expression of the disease in a given population.
What is acute rheumatic fever and rheumatic heart disease? An explainer video for school staff
Rheumatic carditis is a term used to describe active inflammation of the myocardium, endocardium and pericardium that occurs in rheumatic fever. While myocarditis and pericarditis may both occur in rheumatic fever, the predominant manifestation of carditis is the involvement of the endocardium presenting as a valvulitis that predominantly affects the mitral and aortic valves.
Joint involvement occurs in approximately 75% of cases of primary rheumatic fever. The classic history of joint involvement in acute rheumatic fever is one of large joint migratory polyarthritis. The inflammation lasts about two to three days in each joint and most often resolves without any sequelae.
In 5% to 10% of rheumatic fever patients, chorea, which is also known as Sydenham's chorea, can be a part of the acute presentation. Still, this complication may also occur as an isolated finding up to 6 months after the initial infection with group A streptococcus. Atypical behavior such as restlessness and crying can also be observed. In fact, sometimes even a transient psychosis is noted in patients with rheumatic fever.
Both subcutaneous nodules and erythema marginatum are less common manifestations of acute rheumatic fever, both of which are most often linked to a greater chance of developing carditis. Nodules in acute rheumatic fever are smaller and shorter-lived than the nodules of rheumatoid arthritis. Erythema marginatum represents a rash that is usually present over the trunk and rarely seen over the face.