sábado, 23 de febrero de 2019

What is Rheumatic Fever?

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Rheumatic fever (usually referred to as acute rheumatic fever) represents delayed, non-suppurative consequence of a pharyngeal infection with the group A streptococcus. Group A streptococcus contains a myriad of cell surface components; since some of them are molecularly similar to human tissues (such as heart valve tissue), a harmful immune response can ensue.

Following a latent period of two to three weeks after the initial pharyngitis, first signs or symptoms of rheumatic fever can slowly emerge. The disease usually has 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 is specific for children between 5 and 15 years of age, it can be found in any age.

Reliable data on the incidence of rheumatic fever are scarce. Still, it is estimated that globally there are 470 thousand new cases of rheumatic fever and 233 thousand deaths each year attributable to this condition. The mean incidence of acute rheumatic fever is 19 per 100,000 population, with most of the cases occurring in developing countries and among indigenous groups.

In the developed countries there is much lower incidence of rheumatic fever at 2 to 14 cases per 100,000 population, most likely due to good hygienic practices and routine use of antibiotics for acute pharyngitis. It is well established that environmental and socioeconomic factor play an indirect, but essential role in the magnitude and severity of this condition.

During epidemics of the disease in the mid-1900s, as many as 3 percent 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 given population.

Clinical features

Rheumatic carditis is a term designating 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 – particularly affecting 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 patients, chorea (also known as Sydenham's chorea) can be a part of the acute presentation. Still, it 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 be observed, and sometimes even a transient psychosis is noted.

Both subcutaneous nodules and erythema marginatum are less common manifestations of acute rheumatic fever, most often linked to a greater chance of developing carditis. Nodules in acute rheumatic fever are smaller and shorter lived than the nodules of the rheumatoid arthritis. Erythema marginatum represents a rash that is usually present over the trunk, and rarely seen over the face.