Acute Rheumatic Fever in Children: Diagnostic Criteria

Acute rheumatic fever (ARF) is a common diagnostic problem in developing countries. The incidence of ARF (acute rheumatic fever) in developed countries is well under control. Joint pain can be common problem in children but may rarely be symptom of serious joint disease. The physician must be able to determine whether the pain is a result of some lifestyle disorder or of some serious problem within the joints. Juvenile rheumatoid arthritis or rheumatic fever may also be a cause of joint pains and should always be ruled out. Complex and variable presentation of this devastating disorder sometimes confuse the physicians to reach at a diagnosis clinically.

Signs & symptoms and clinical history:

The spectrum of diagnoses that need to be considered can be narrowed down on the basis of clinical history. Age, sex and the acute or insidious mode of onset and development of joint pains act as pointers of the clinical history's role in diagnosis of the rheumatic fever or juvenile rheumatoid arthritis. The diagnostic workup of a child demands a history of preceding or concurrent illness presenting with sore throat or viral symptoms, or a history of recent immunization for rubella or other viral infections. The location, pattern and duration of joint pain are other important points to be taken into consideration.

Diagnostic criteria:

The diagnosis of rheumatic fever is very complicated as the disease may affect a number of organs and tissues. The fact is that no single laboratory test or clinical manifestation is enough to be diagnostic. A composite understanding of clinical manifestations and laboratory investigations is essential to reach at a diagnosis of ARF. If supported by the evidence of preceding Group-A Streptococcal infection, the presence of two major manifestations or one major and two minor manifestations is must to make a diagnosis of rheumatic fever.

1) Major manifestations: As proposed by the American Heart Association, the major manifestations of acute rheumatic fever are clinical evidences of this disease. The major manifestations are: carditis polyarthritis, chorea, erythema marginatum and
subcutaneous nodules. The arthritis/polyarthritis is the most common major manifestation found in the majority (around 75%) of patients during the acute stage of the disease and the remainder being found in relatively small proportion (around 25%) of patients. The arthritis is painful with the joints being swollen, red and warm to touch. Ankles, knees, elbows and wrists are usually involved. Rheumatic carditis is the most serious manifestation of acute rheumatic fever and may affect around 5% of patients with ARF. Chorea means rapid, purposeless involuntary movements of various body parts, generally bilateral and accompanied by muscle weakness. Around 15% of the patients with rheumatic fever may show the signs of chorea. The rash of rheumatic fever is called Erythema marginatum and is nonpruritic, nonindurated and pink rash. Lesions may vary in size and occur mainly on the trunk, buttocks and proximal extremities and occurs in around 5% of patients with rheumatic fever. Subcutaneous nodules are firm, painless nodules and may appear over some joints in about 1% of patients with rheumatic fever.

2) Minor manifestations and laboratory investigations: The minor manifestations of rheumatic fever are: history of previous rheumatic fever or rheumatic heart disease, arthralgia, fever, elevated acute phase proteins and prolonged P-R intervals on Electrocardiogram (ECG). The minor manifestations tend to be less specific than the major manifestations discussed above. The laboratory studies such as detection of elevated levels of acute phase reactants are also nonspecific. Differential count of white blood cells may show granulocytosis in patients having acute streptococcal infection. Fever is always present at the onset of an attack of rheumatic fever. The temperature is usually around 102^o F (39^o C) at the onset and may persist at around 100^o F (37.8^o C) for several weeks. Arthralgia means the presence of joint pain in one or more joints without inflammation, tenderness or limitation of range of motion of a joint. If polyarthritis has already been counted as major manifestation, arthralgia should be ignored. Elevated levels of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and fibrinogen are generally observed in untreated patients with rheumatic fever. These are nonspecific indicators of inflammation and neither ESR nor CRP is specific for rheumatic fever. Prolongation of P-R interval on ECG usually indicates an abnormal delay in conduction through the atrioventricular (AV) node. P-R interval prolongation on ECG is observed in around 35% of patients with rheumatic fever but may also be present in other inflammatory diseases (Myocarditis and digitalis or quinidine toxicity may also cause prolonged P-R intervals on ECG). A throat swab culture should always be done to isolate Group-A Streptococcal infection at the time of diagnosis of acute rheumatic fever. It is better if antistreptolysin-O (ASO) titers are measured in these patients. Elevated levels of antistreptolysin-O (ASO) titers are observed in approximately 80% of patients
affected by rheumatic fever. An ASO titer of over 300 units in a school-age child is an evidence of recent Group-A Streptococcal infection.

Differential diagnosis:

Non-rheumatic conditions that present with musculo-skeletal pain in children can usually be diagnosed on the basis of physical examination and history without any laboratory investigation. Such conditions could be trauma, hypermobility syndrome, overuse syndrome, benign recurrent limb pains and psychogenic rheumatism. Rheumatic fever, juvenile rheumatoid arthritis, infectious and neoplastic bone disease as causative agents of joint pains need to be evaluated in the light of major and minor manifestations discussed above.