Sydenham's Chorea

Diagnosis

A diagnosis of Sydenham's chorea is primarily based upon a thorough clinical evaluation, detection of characteristic symptoms and findings, and a careful patient history. Because the initial illness (e.g., pharyngitis) may precede the onset of chorea by as much as 6 months or more, many patients (or their parents) may not provide a history of streptococcal infection. In addition, there may be minimal or no evidence of recent infection with group A streptococci. Evidence of recent streptococcal infection may include...

Elevated levels of certain antibodies to streptococci (e.g., antistreptolysin O [ASO] or other antistreptococcal antibodies) in the blood. Although up to 80 percent of patients with ARF have elevated levels of ASO, many individuals with Sydenham's chorea may have negative results with such testing.
A positive throat culture. A throat culture involves swabbing the back of the throat with a sterile applicator to obtain material for laboratory analysis that may help to identify certain bacteria, including group A beta-hemolytic streptococci. Throat cultures are often negative by the time of symptom onset in those with ARF. Conversely, up to 60% to 80% of healthy teenagers may have an asymptomatic positive throat culture. Therefore, the specificity and sensitivity of this test is very low.
Elevated erythrocyte sedimentation rate (ESR). ESR, also known as the "sed rate," is a laboratory test that measures the rate at which red blood cells (erythrocytes) settle to the bottom of a specialized test tube, leaving the fluid portion of the blood at the top of the tube. This test serves as a nonspecific indicator of inflammation, since red blood cells tend to clump together and settle more quickly to the bottom of the blood sample when inflammation is present. ESR may also be used to help adjust dosage levels of anti-inflammatory drugs during treatment of patients with certain inflammatory diseases. Although the ESR may remain elevated in those with ARF for months, the results may be normal in some patients who initially receive medical attention due to the sole or late manifestation of Sydenham's chorea.

As mentioned earlier, chorea may or may not occur in association with other symptoms and findings associated with acute rheumatic fever (ARF). In addition, there is no single clinical feature or laboratory test that definitively establishes a diagnosis of ARF. Instead, the presence of certain clinical findings, termed "Jones criteria," suggests a probable diagnosis of ARF. The most current, revised Jones criteria for the diagnosis of ARF (revised in 1992 by the American Heart Association) include confirmation of 2 major criteria or 1 major and 2 minor criteria, in addition to evidence of recent streptococcal group A infection. Major criteria include migratory polyarthritis, carditis, erythema marginatum, subcutaneous nodules, and chorea. (For further information, please see the section entitled "Symptoms/Findings.") Minor criteria include less specific findings, such as fever; joint discomfort (arthralgia) in the absence of redness, warmth, or pain upon physical examination; and certain findings detected by diagnostic tests. These include...

An elevated ESR (see above)
Elevated levels of C-reactive protein (CRP) in the blood. Levels of CRP rise in response to inflammation, thus serving as a nonspecific indicator of an inflammatory process. As with ESR, CRP levels may be used to help adjust dosage levels of anti-inflammatory drugs used to help treat certain inflammatory diseases.
Prolonged P-R interval on an electrocardiogram (ECG), which is a diagnostic test that records electrical activity of heart muscle (myocardium). This is a nonspecific finding in which an ECG records a slightly increased delay between contractions of the upper and lower chambers of the heart.

Experts indicate that some patients may be diagnosed with acute rheumatic fever in the absence of the criteria described above. Such exceptions to the Jones criteria include those patients with...

Chorea (i.e., Sydenham's chorea), if other possible causes of choreic movements have been excluded
Late-onset or insidious carditis with no other likely cause

In addition, a recurrence of ARF should be considered in those with prior rheumatic fever or rheumatic valvular heart disease and evidence of a recent preceding streptococcal infection with 1 major or 2 minor criteria.

Thus, again, a diagnosis of Sydenham's chorea is generally based upon characteristic symptoms and findings and a complete patient history, revealing a relatively recent onset of symptoms. Diagnostic evaluation may include clinical assessments to detect certain signs potentially associated with chorea, such as an inability to maintain protrusion of the tongue or a finding known as "relapsing grip" (or "milking sign"). To detect the latter, the physician asks the patient to squeeze his or her (i.e., the examiner's) hand; in those with Sydenham's chorea, the patient's grip may continuously, erratically increase and decrease.

For some patients, neurologic assessment may include certain neuroimaging studies, such as magnetic resonance imaging (MRI). In those with Sydenham's chorea, EEG results are frequently abnormal, with irregular slowing of certain brain wave patterns. Also, as mentioned previously, MRI may reveal increased size of certain regions of the basal ganglia or other findings.

Once a diagnosis of Sydenham's chorea is considered, a thorough cardiac evaluation should also be conducted to rule out or confirm possible cardiac involvement. Such assessment includes evaluation of heart and lung sounds through use of a stethoscope to detect new or changing cardiac murmurs that may result from altered blood flow through certain heart valves. X-ray imaging may reveal enlargement of the heart (cardiomegaly), a finding commonly seen in those with significant carditis. In addition, more sensitive techniques may be conducted to record the heart's electrical activity (electrocardiography) and to create an image of the structure of the heart through the use of reflected sound waves (echocardiography), thereby assisting physicians in detecting and characterizing structural or functional abnormalities of the heart.

The differential diagnosis of Sydenham's chorea includes chorea associated with systemic lupus erythematosus (SLE) or other post-infectious choreas (particularly in relationship with viral infections). Other considerations include familial forms of chorea, exposure to particular toxins, the use of certain medications, central nervous system lesions, or other conditions that may be associated with similar symptoms or findings.