Sydenham Chorea or Primary Antiphospholipid Syndrome?

Sir,

We appreciate the comment of Al-Matar et al. On emphasising Sydenham chorea as an important differential diagnosis to chorea in primary antiphospholipid syndrome (PAPS), they raised an important issue. Both conditions have been proposed as sharing similar pathogenetic mechanisms involving antineuronal antibodies [[5], [8]]. Actually, it may be difficult to differentiate these diseases without an extensive laboratory work-up and long-term monitoring of given patients. According to the modified Jones criteria [[2]] Sydenham chorea is the exclusion diagnosis suitable even in the absence of specific confirmatory findings, and PAPS ranks among the various other diagnoses to be ruled out.

As to our patients [[6]], several lines of evidence are in conflict with the diagnosis of Sydenham chorea: 1. Two patients had typical features of PAPS distinct from chorea, even if these abnormalities were only mildly expressed: One exhibited thrombocytopenia while the other experienced steadily deteriorating valvulitis and, recently, an episode of spontaneous cerebral venous sinus thrombosis; 2. Although aCL antibodies may temporarily occur at high titers in rheumatic fever [[4]] long-term persistence, as required for the diagnosis of PAPS, has not yet been reported. In the series of patients from Chile cited by Al-Matar and co-workers levels of aCL antibodies of patients with Sydenham chorea normalised within 132 days after disease onset [[4]]. Other investigators altogether failed to find high aCL antibody levels in patients with rheumatic fever [[1], [3], [7]]. Furthermore, presence of lupus anticoagulant is an unusual finding in rheumatic fever. Our patients all showed consistently elevated aCL antibody titers for ≥ six months and one was positive for the lupus anticoagulant [[6]].

In all, according to the current diagnostic criteria the illness of our patients must be classified as PAPS. We agree, however, with Al-Matar et al that whenever uncertainties remain about the correct diagnostic attribution (e.g. at the first visit), antibiotic prophylaxis should not be denied.

References

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• 2 Dajani A S, Ayoub E, Bierman F Z, Bisno A L, Denny F W, Durack D T. et al . Guidelines for the diagnosis of rheumatic fever: Jones Criteria, updated 1992, American Heart Association.  Circulation. 1993;  87 302-307
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