Acute rheumatic fever
ARF occurs within 10 days to six weeks after an episode of GAS pharyngitis, although the causative infection may be subclinical. It occurs as a nonsuppurative complication of GAS pharyngitis in susceptible hosts. While the underlying mechanisms of ARF are not well understood, the key event is inappropriate activation of the immune system, leading to autoimmune attack.
Invading pathogens trigger innate immune responses, leading to inflammation. During the inflammatory response, immune cells are attracted to the site of infection and are exposed to antigenic compounds. Antigenic compound in GAS infections include the M-protein, hyaluronic acid coat and exotoxins.
the presentation of an antigen to the cells of the immune system (T-lymphocytes) is mediated by the human leucocyte antigen (HLA) system are leads to the production of antibodies and memory cells. HLA genes are subject to variation : the incidence of ARF is associated with certain types of HLA complexes. GAS antigens, in particular M-protein, associated with HLA, mimic protein complexes of host tissue and trigger cross-reactivity. The antibodies produced against GAS begin to attack host-tissue.
GAS M-protein antigens mimic myosin found in cardiac muscle and other types of extracellular protien. the causes an immune attack againt cardiac, subcutaneous and central nervous tissues and the joints. Infiltration of T-lymphocytes and macrophages leads to pain and inflammation, with subsequent fibrosis and scrring. It is important to note there are no bacteria present in these inflammation sites.
Diagnosis is based on the modified Jones criteria. The presence of two major symtoms, or one major and two minor, are required to diagnose ARF
Major symptoms
Arthritis: This is the most common presenting symptom of ARF, occurring in three quarters of initial attacks. Classically, presentation is in the form of migratory polyarthritis-inflammation occurs in one or more joints, is present for two to three days and subside as it the moves to another joint, arthritis may be confined to a single joint. The knees and ankles are most often affected, although the inability to weight-bear is indicative of hip joint involvement. An attack may last up to three weeks, resolving with no residual impairment of function. Arthritis manifests as redness, heat and swelling of the joint with limited movement. It is often very painful.
Carditis: Inflammation of the heart (carditis) affects all layers of the heart, although it is inflammation of the endocardium - the innermost layer, including the valves - that has the most adverse consequences. The development of a murmur, due to valve dysfunction, may be the only sign of cardiac inflammation. However, echocardiography may be used to confirm carditis. Chest pain and friction rub (a high frequency scratching or squeaking sound made by the inflamed pericardial membranes) may occur as a result of pericarditis.
Chorea: Sydenham's chorea (also called St Vitus Dance) is uncoordinated jerking movement of the hands, feet, face and tongue. It occurs more commonly in girls. It lasts between six weeks and six months, with on permanent neurological damaged; however recurrence is associated with pregnancy and oral contraceptive use.
Erythema marginatum: the appearance of pink macules on the trunk and limbs is a rare sign of ARF. This rash is transient. painless, and not itchy, and may deepen with heat. The centre of the macule may fade to generate pink rings that can be mistaken for ringworm.
Subcutaneous nodules: Painless, firm lumps that appear over the bony prominences or along the track of extensor tendons are a rare sign of ARF. These do not affect function and resolve within one to two weeks of noset.
Minor symptoms include: fever, joint pain, increased C-reactive protein and prolonged PR interval on ECG.
Rheumatic heart disease.
Following the initial attack, ARF can be reactivated by subsequent exposure to GAS. The development of rheumatic heart disease (RHD) may occur over years or even decades, as recurrent inflammation of the endocardium, and especially the heart valves, leads to increased fibrosis and scarring. The valves of the heart become permanently thickened and retracted, and leaflets (flaps of the heart valves) may adhere to each other. This stenosis of the valves causes dysfunction, with regurgitation and reduced opening.
The mitral valve (between the left atrium and ventricle) is most commonly affected, although 25 percent of people with RHD have mitral and aortic valve involvement. Valves in the right side of the heart are only rarely involved.As the aortic valve become increasingly dysfunction (AF) develops, The combination of stagnation of flow and AF may generate thombosis, leading to strokes. It also causes increasing pressure in the pulmonary circulation and ventricular hypertrophy that eventually leads to heart failure.
Deformation of the valves increases a person's risk of developing infective endocarditis. Bacteria penetrating the blood stream can seed on the roughened surfaces of the valves. Here they may trigger acute, or, more frequently, chronic inflammation that leads to the development of friable vegetative growths on the valve flaps. These growths are composed of fibrin, inflammatory cells and bacteria, and can embolise or cause further deterioration in valves function. Common causative organisms are streptococcus viridans and other bacteria that form part of the normal flora of the mouth. These may penetrate the bloodstrem during dental care, making prophylactic antibiotic therapy essential for people with RHD undergoing dental procedures.
Mortality rate for RHD in regions with no access to treatment can be as high as 20 per cent within six years of diagnosis, due to severe heart failure. Pregnancy is particularly associated, the aim is to reduce complication of RHD - treating heart failure and AF, and reducing the risks of thromboembolism and infective endocarditis. Once valve disease becomes symptomatic, valves need to be repaired or replaced. Treatment of RHD is costly and uses a lot of resources - prevention is evidently farmore cost-effective for both developed and developing nations.
Acute rheumatic fever
ARF occurs within 10 days to six weeks after an episode of GAS pharyngitis, although the causative infection may be subclinical. It occurs as a nonsuppurative complication of GAS pharyngitis in susceptible hosts. While the underlying mechanisms of ARF are not well understood, the key event is inappropriate activation of the immune system, leading to autoimmune attack.
Invading pathogens trigger innate immune responses, leading to inflammation. During the inflammatory response, immune cells are attracted to the site of infection and are exposed to antigenic compounds. Antigenic compound in GAS infections include the M-protein, hyaluronic acid coat and exotoxins.
the presentation of an antigen to the cells of the immune system (T-lymphocytes) is mediated by the human leucocyte antigen (HLA) system are leads to the production of antibodies and memory cells. HLA genes are subject to variation : the incidence of ARF is associated with certain types of HLA complexes. GAS antigens, in particular M-protein, associated with HLA, mimic protein complexes of host tissue and trigger cross-reactivity. The antibodies produced against GAS begin to attack host-tissue.
GAS M-protein antigens mimic myosin found in cardiac muscle and other types of extracellular protien. the causes an immune attack againt cardiac, subcutaneous and central nervous tissues and the joints. Infiltration of T-lymphocytes and macrophages leads to pain and inflammation, with subsequent fibrosis and scrring. It is important to note there are no bacteria present in these inflammation sites.
Diagnosis is based on the modified Jones criteria. The presence of two major symtoms, or one major and two minor, are required to diagnose ARF
Major symptoms
Arthritis: This is the most common presenting symptom of ARF, occurring in three quarters of initial attacks. Classically, presentation is in the form of migratory polyarthritis-inflammation occurs in one or more joints, is present for two to three days and subside as it the moves to another joint, arthritis may be confined to a single joint. The knees and ankles are most often affected, although the inability to weight-bear is indicative of hip joint involvement. An attack may last up to three weeks, resolving with no residual impairment of function. Arthritis manifests as redness, heat and swelling of the joint with limited movement. It is often very painful.
Carditis: Inflammation of the heart (carditis) affects all layers of the heart, although it is inflammation of the endocardium - the innermost layer, including the valves - that has the most adverse consequences. The development of a murmur, due to valve dysfunction, may be the only sign of cardiac inflammation. However, echocardiography may be used to confirm carditis. Chest pain and friction rub (a high frequency scratching or squeaking sound made by the inflamed pericardial membranes) may occur as a result of pericarditis.
Chorea: Sydenham's chorea (also called St Vitus Dance) is uncoordinated jerking movement of the hands, feet, face and tongue. It occurs more commonly in girls. It lasts between six weeks and six months, with on permanent neurological damaged; however recurrence is associated with pregnancy and oral contraceptive use.
Erythema marginatum: the appearance of pink macules on the trunk and limbs is a rare sign of ARF. This rash is transient. painless, and not itchy, and may deepen with heat. The centre of the macule may fade to generate pink rings that can be mistaken for ringworm.
Subcutaneous nodules: Painless, firm lumps that appear over the bony prominences or along the track of extensor tendons are a rare sign of ARF. These do not affect function and resolve within one to two weeks of noset.
Minor symptoms include: fever, joint pain, increased C-reactive protein and prolonged PR interval on ECG.
Rheumatic heart disease.
Following the initial attack, ARF can be reactivated by subsequent exposure to GAS. The development of rheumatic heart disease (RHD) may occur over years or even decades, as recurrent inflammation of the endocardium, and especially the heart valves, leads to increased fibrosis and scarring. The valves of the heart become permanently thickened and retracted, and leaflets (flaps of the heart valves) may adhere to each other. This stenosis of the valves causes dysfunction, with regurgitation and reduced opening.
The mitral valve (between the left atrium and ventricle) is most commonly affected, although 25 percent of people with RHD have mitral and aortic valve involvement. Valves in the right side of the heart are only rarely involved.As the aortic valve become increasingly dysfunction (AF) develops, The combination of stagnation of flow and AF may generate thombosis, leading to strokes. It also causes increasing pressure in the pulmonary circulation and ventricular hypertrophy that eventually leads to heart failure.
Deformation of the valves increases a person's risk of developing infective endocarditis. Bacteria penetrating the blood stream can seed on the roughened surfaces of the valves. Here they may trigger acute, or, more frequently, chronic inflammation that leads to the development of friable vegetative growths on the valve flaps. These growths are composed of fibrin, inflammatory cells and bacteria, and can embolise or cause further deterioration in valves function. Common causative organisms are streptococcus viridans and other bacteria that form part of the normal flora of the mouth. These may penetrate the bloodstrem during dental care, making prophylactic antibiotic therapy essential for people with RHD undergoing dental procedures.
Mortality rate for RHD in regions with no access to treatment can be as high as 20 per cent within six years of diagnosis, due to severe heart failure. Pregnancy is particularly associated, the aim is to reduce complication of RHD - treating heart failure and AF, and reducing the risks of thromboembolism and infective endocarditis. Once valve disease becomes symptomatic, valves need to be repaired or replaced. Treatment of RHD is costly and uses a lot of resources - prevention is evidently farmore cost-effective for both developed and developing nations.
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