Rheumatic
fever is an inflammatory disease that occurs following a Streptococcus pyogenesinfection, such as strep throat or scarlet fever. Believed to be caused by antibody cross-reactivity that can involve the heart, joints, skin, and brain, the illness typically develops two
to three weeks after a streptococcal infection. Acute rheumatic fever commonly
appears in children between the ages of 5 and 17, with only 20% of first-time
attacks occurring in adults. The illness is so named because of
its similarity in presentation to rheumatism.
Diagnosis:
Modified Jones criteria were first published in 1944 by T.
Duckett Jones, MD. They have been periodically revised by the American Heart Association in collaboration with other
groups. According to revised Jones criteria, the diagnosis of rheumatic fever
can be made when two of the major criteria, or one major criterion plus two
minor criteria, are present along with evidence of streptococcal infection:
elevated or rising antistreptolysin O titre or DNAase. Exceptions arechorea and indolent carditis, each of which by itself can
indicate rheumatic fever.
Major
criteria
§ Migratory
polyarthritis:
a temporary migrating inflammation of the large joints, usually starting in the
legs and migrating upwards.
§ Carditis: inflammation of the heart muscle
which can manifest as congestive heart failure with shortness of breath, pericarditis with a rub, or a new heart
murmur.
§ Subcutaneous nodules: painless, firm
collections of collagen fibers over bones or tendons. They commonly appear on the back
of the wrist, the outside elbow, and the front of the knees.
§ Erythema marginatum: a long lasting rash that begins on the trunk or
arms as macules and spreads outward to form a
snake like ring while clearing in the middle. This rash never starts on the
face and it is made worse with heat.
§ Sydenham's chorea (St. Vitus' dance): a characteristic series of rapid
movements without purpose of the face and arms. This can occur very late in the
disease.
Minor
criteria
§ Fever
§ Arthralgia: Joint pain without swelling
(Cannot be included if polyarthritis is present as a major symptom)
§ ECG showing features of heart
block, such as
a prolonged PR
interval (Cannot be included if
carditis is present as a major symptom)
§ Previous episode of rheumatic fever
or inactive heart disease
Other
signs and symptoms
PATHOPHYSIOLOGY:
Rheumatic fever is
a systemic disease affecting the peri-arteriolar connective tissue and can
occur after an untreated Group A Beta hemolytic streptococcal pharyngeal
infection. It is believed to be caused by antibody cross-reactivity.
This cross-reactivity is a Type II hypersensitivity reaction and is termed molecular mimicry. Usually, self reactive B cells remain
anergic in the periphery without T cell co-stimulation. During a Streptococcus
infection, mature antigen presenting cells such as B cells present the
bacterial antigen to CD4-T cells which differentiate into helper T2 cells. Helper T2cells
subsequently activate the B cells to become plasma cells and induce the
production of antibodies against the cell wall of Streptococcus. However the
antibodies may also react against the myocardium and joints, producing the symptoms of rheumatic
fever.
Group A streptococcus pyogenes has a cell wall composed of branched polymers which sometimes contain M protein that are highly antigenic.
The antibodies which the immune system generates against the M protein may
cross react with cardiac myofiber protein myosin,heart muscle glycogen and smooth muscle cells of arteries,
inducing cytokine release and tissue destruction.
However, the only proven cross reaction is with perivascular connective
tissue.[citation needed] This inflammation occurs through
direct attachment of complement and Fc receptor-mediated recruitment of
neutrophils and macrophages. Characteristic Aschoff
bodies, composed of swollen eosinophilic collagen surrounded by
lymphocytes and macrophages can be seen on light microscopy. The larger
macrophages may become Aschoff giant cells. Acute rheumatic valvular lesions
may also involve a cell-mediated immunity reaction as these lesions
predominantly contain T-helper cells and macrophages.
In acute rheumatic
fever, these lesions can be found in any layer of the heart and is hence called
pancarditis. The inflammation may cause a serofibrinous pericardial exudate
described as "bread-and-butter" pericarditis,
which usually resolves without sequelae. Involvement of the endocardium
typically results in fibrinoid necrosis and verrucae formation along the lines
of closure of the left-sided heart valves. Warty projections arise from the
deposition, while subendothelial lesions may induce irregular thickenings
called MacCallum plaques.
Chronic rheumatic
heart disease is characterized by repeated inflammation with fibrinous resolution.
The cardinal anatomic changes of the valve include leaflet thickening,
commissural fusion and shortening and thickening of the tendinous cords
Treatment:
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