Clinical Scenario:
An 11-year-old girl is brought to the emergency department with a 3-week history of progressively worsening involuntary movements, initially involving her head and neck and subsequently affecting all four limbs. The movements have become severe enough to interfere with walking, writing and other daily activities. There is no history of loss of consciousness or seizures.
On examination, she has irregular, unpredictable, non-rhythmic movements involving the face, neck and limbs. The movements become more prominent during voluntary activity and disappear during sleep. She has no focal neurological deficit.
Which of the following is the most appropriate investigation to support the suspected diagnosis?
A. Antistreptolysin O (ASO) titre and anti-DNase B antibodies
B. Cerebrospinal fluid examination
C. Electroencephalography
D. Magnetic resonance imaging of the brain
E. Serum ceruloplasmin level
Correct answer & Explanation:
Correct answer: A. Antistreptolysin O (ASO) titre and anti-DNase B antibodies
Explanation
The clinical picture is highly suggestive of Sydenham chorea, a major manifestation of acute rheumatic fever.
The most appropriate investigations to look for evidence of a preceding Group A Streptococcus infection include ASO and anti-DNase B antibody titres. However, an important postgraduate point is that streptococcal antibody titres may be normal by the time chorea develops, because Sydenham chorea often has a prolonged latent period after the initial infection. Therefore, a negative titre does not exclude Sydenham chorea.
The evaluation should also include assessment for subclinical carditis, particularly echocardiography, because carditis may be clinically silent.
Why the other options are less appropriate
- B. CSF examination: Not routinely required when the clinical picture is typical of Sydenham chorea and there are no features suggesting CNS infection.
- C. EEG: There is no history of seizures or altered consciousness to suggest an epileptic disorder.
- D. MRI brain: Neuroimaging is not routinely required in typical Sydenham chorea but may be considered when the presentation is atypical or another structural neurological disorder is suspected.
- E. Serum ceruloplasmin: Wilson disease should be considered in appropriate cases of acquired movement disorder, particularly with hepatic or other neurological features, but the acute/subacute presentation in this clinical context is more suggestive of Sydenham chorea.
Reference:
Gewitz MH, Baltimore RS, Tani LY, Sable CA, Shulman ST, Carapetis J, et al. Revision of the Jones Criteria for the diagnosis of acute rheumatic fever in the era of Doppler echocardiography: a scientific statement from the American Heart Association. Circulation. 2015;131(20):1806-18.
