What is acute rheumatic fever?
Acute rheumatic fever (ARF) is caused by a reaction to a bacterial infection with particular strains of group A streptococcus. It has long been thought that ARF only follows streptococcal pharyngitis (sore throat), however recent studies from Aboriginal populations in Australia have suggested streptococcal skin infection may precede some cases of ARF. Those who have experienced one episode of ARF are more likely to suffer recurrent attacks with subsequent group A streptococcal infections.
The skin sign of acute rheumatic fever is erythema marginatum.
Who gets rheumatic fever?
ARF usually affects children aged 5–15 years. Most cases of ARF currently occur in developing countries. Worldwide there is an estimated 470 000 new cases of ARF annually (60% of whom eventually develop rheumatic heart disease). In most developed countries ARF is now rare, with a few notable exceptions; the highest documented rates of ARF in the world are in Maori and Pacific people in New Zealand, Aboriginal Australians, and those in Pacific Island nations.
Rheumatic fever is associated with poverty, overcrowding and poor sanitation facilities. It is suspected that there are genes that make some families more susceptible to the disease.
What are the clinical features of acute rheumatic fever?
Symptoms of ARF generally develop several weeks after an episode of streptococcal pharyngitis. However, many patients do not recall having a sore throat. Non-specific symptoms include:
- Abdominal pain
- Muscle aches
ARF causes a variety of more specific clinical features:
- Polyarthritis (multiple inflamed joints) — Most often ankles, knees, elbows, wrists. Arthritis can migrate from one joint to another.
- Carditis (inflammation of the heart) – This involves the heart valves, heart muscle, and membrane surrounding the heart.
- Sydenham chorea – This is a disorder of the nervous system characterised by personality changes, muscle weakness, and involuntary movements.
Skin signs in ARF may include:
- Erythema marginatum rheumaticum – This is a characteristic type of annular erythema that occurs in about 10% of first attacks of ARF in children; it is very rare in adults. The rash can be difficult to detect in dark-skinned people. When present, it is found on the trunk and upper arms and legs, but almost never on the face, palms or soles. The rash appears as pink or red macules (flat spots) or papules (small lumps), which spread outwards in a circular shape. As the lesions advance, the edges become raised and red, and the centre clears. The lesions are not itchy or painful, and sometimes go unnoticed by the patient. The lesions can fade and reappear within hours, reappearing in hot conditions. Erythema marginatum may persist intermittently for weeks to months, even after successful treatment of ARF.
- Subcutaneous nodules (small lumps under the skin) – These are uncommon, occurring in less than 2% of patients with ARF. The painless nodules are found over joints (such as the elbows, knees, ankles, and knuckles), the back of the scalp, and the vertebrae (backbone). The nodules are firm, round, mobile, and range from 0.5-2 cm in size. The nodules are usually only found when severe carditis is present. They usually resolve within one month but may persist for longer.
What are the complications of acute rheumatic fever?
The most severe complication of recurrent ARF is permanent damage to heart valves, known as rheumatic heart disease. The disease can result in permanent damage to:
- Heart valves, particularly the mitral valve and aortic valve, which can lead to valvular stenosis and/or regurgitation.
- Heart muscles, reducing pumping action ie causing heart failure.
- The membrane around the heart, causing pericarditis.
- Irregular heart rhythms, such as atrial fibrillation.
How is acute rheumatic fever diagnosed?
The diagnosis of ARF is challenging, as there are no clinical features or diagnostic tests available to confirm or rule out this condition. Instead, the diagnosis is made using the Jones criteria. These criteria require evidence of a preceding group A streptococcus infection, and various combinations of the characteristic features above and other non-specific clinical features. A detailed explanation of these criteria (and modifications for the New Zealand environment) can be found on the National Heart Foundation of New Zealand website.
Tests to confirm evidence of a group A streptococcal infection include:
- Blood tests to look for elevated or rising antibodies to group A streptococcus. The most commonly used tests are the plasma antistreptolysin O and the antideoxyribonuclease B titres.
- Culture of throat swabs and rapid antigen tests for group A streptococcus are less accurate.
Other tests used in the assessment of a patient with suspected ARF include:
- Blood tests – markers of inflammation, such as ESR or CRP, may be raised
- Electrocardiogram and echocardiogram to identify heart involvement
- Doppler and colour flow mapping to detect minor valvular defects not evident clinically
What is the treatment for rheumatic fever?
Following a diagnosis of rheumatic fever, it is standard practice to treat the group A streptococcal infection that led to the disease with oral penicillin (although this practice has not been proven to alter long-term outcomes).
Following the initial attack, patients are treated with continuous penicillin to prevent further streptococcal colonisation or infection and additional damage to the heart. Continuous penicillin is also recommended for people with established rheumatic heart disease. Continuous penicillin is generally given by injection every four weeks for a minimum of 10 years. Some patients, such as those with severe carditis, may require lifelong treatment.
Aspirin or naproxen are added to reduce inflammation, fever and pain. In extreme cases, a corticosteroid such as prednisone may be added.
Patients with rheumatic heart disease may occasionally require heart surgery to repair or replace damaged heart valves.
Can rheumatic fever be prevented?
ARF can be prevented with timely treatment of group A streptococcal pharyngitis, particularly in people aged 5-15 years. People with sore throat and fever should see the doctor for advice. Vaccines are currently in development and are eagerly awaited.