Rheumatic fever

RheumaticAcute rheumatic fever is a multisystemic inflammatory disorderan illness caused by type II hypersensitivityan immunological reaction following group A beta haemolyticstreptococcal infection. 

Epidemiology

Acute rheumatic fever is most common in children aged 5 to 15 years. It is most common in developing nations where antibiotic prescription is low ¹.

Clinical presentation

Joint pain and swelling is the most common presenting feature. Sydenham's chorea, which is an uncoordinated jerky movement of the face, feet and hands, is also common. Carditis may be present as valvulitis producing a new murmur (most common), myocarditis leading to cardiac enlargement and even decompensation and pericarditis leading to a pericardial rub and effusion. Erythema marginatum and subcutaneous nodules are much rarer. Fever is present in most cases ¹.

Group A streptococcal throat infection has classically been attributed as causing bouts of rheumatic fever, although group A streptococcal skin infections have also been proposed as being able to cause disease ². Symptoms appear weeks after the initial infection ¹.

Pathology

Acute rheumatic fever occurs as a result of molecular mimicry where antibodies and T cells that react against the M cell wall protein of the group A streptococcus pharyngeal infectionbacteria react against various proteins in the body (eg. Cross reactionmyosin in cardiac tissue).

The binding of these auto-reactive antibodies against protein M with otherand cells glycoproteins leads to involvementinflammation and further damage. The subsequent Th2 cell activation in the convalescence period of other organs such as heart.  

Pathology

It principally involvesan acute episode triggers fibrosis that can lead to the heart (pancarditis can result), joints (see article: Jaccoud arthropathy), central nervous system, skin,long term complications and subcutaneous tissuethe development of rheumatic heart disease ³.

Not all group A streptococcal bacteria are capable of producing rheumatic fever likewise not all patients with a group A streptococcus infection develop rheumatic fever, so therefore there are underlying patient susceptibility and bacterial factors that determine if rheumatic fever will occur ¹.

DiagnosisDiagnostic criteria

Jones criteria

Evidence of group A beta haemolytic streptococcus infection (raised anti-Streptolysin O titre, positive throat culture, recent Scarlet fever or positive Streptococcal A antibodies) and 2 major or 1 major and 2 minor criteriascriteria ².

• major criteria
  • migratory polyarthritis
  • pancarditis
  • Sydenham's chorea
  • erythema marginatum
  • subcutaneous nodules
• minor criteria
  • fever
  • arthralgia
  • increase in acute phase reactants (e.g. CRP/ESR)
  • previous episode of rheumatic fever or inactive heart disease
  • leukocytosis
  • ECG changes such as a prolonged PR interval (not if carditis is present as a major symptom)

Histology

• Aschoff bodies
• lymphocytes
• swollen collagen
• plump macrophages (Anitschkow cells): pathognomonic
• Anitschkow cells (caterpillar cells) may be seen which are macrophages with chromatin condensation that can fuse to become multinucleated cells (Aschoff cells)

Radiographic features

Echocardiography

Echocardiography is important for assessing the valves, cardiac function and pericardium of the heart during an episode of acute rheumatic fever and for ongoing follow up. Mitral regurgitation is most commonly seen during an attack episode followed by aortic regurgitation ². Echocardiography plays an important role is diagnosing so-called "silent carditis" where an audible murmur is not heard but there are still signs of regurgitation suggesting valvulitis.

Treatment and prognosis

BenzathineIntramuscular benzathine penicillin 120 IU intramusacular injuection isinjection delivered on a monthly basis, at least 10 years past the drug of choice to eliminatemost recent attack, provides prophylaxis against group A streptococci infection and further bouts of rheumatic fever. While good supportive therapy can reduceAdherence to monthly injections is a large issue ⁴. 

Repetitive episodes of rheumatic fever increases the mortality and morbidityrisk of thedeveloping rheumatic heart disease.

The clinical course can varies greatly, but in general, ~75with 60% of acute rheumatic attacks subside within 6 weekspatients eventually doing so ⁵.