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J Rheumatol. 2012 Feb;39(2):382-8. doi: 10.3899/jrheum.110768. Epub 2011 Dec 15.

Prevalence of annexin A5 resistance in children and adolescents with rheumatic diseases.

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Children's Hospital at Montefiore, Department of Pediatrics, Division of Rheumatology, Bronx, NY 10467, USA.



The underlying mechanism(s) by which antiphospholipid antibodies (aPL) result in thrombosis remains poorly understood. A significant body of evidence has evolved to support the hypothesis that antibody-mediated disruption of an annexin A5 anticoagulant shield may play a role in the pathogenesis; this proposed mechanism has not been previously studied in children.


We investigated the association between aPL and resistance to annexin A5 anticoagulant activity in 90 children with a variety of rheumatic diseases using a novel mechanistic assay, the annexin A5 resistance assay (A5R).


Patients with a diagnosis of primary aPL syndrome, systemic lupus erythematosus, and mixed connective tissue disease demonstrated lower mean A5R levels (p = 0.030), higher prevalence of positive aPL (p < 0.001), and more thrombotic events (p = 0.014) compared to those with other diagnoses. Patients with persistently positive aPL had significantly lower mean A5R compared to patients with no aPL (mean A5R = 203% ± 44% vs 247% ± 35%; p < 0.001), whereas patients with transient aPL did not. Patients with thrombosis had lower A5R levels compared to those without thrombosis (mean A5R = 207% ± 36% vs 237% ± 46%; p = 0.048).


Children and adolescents with rheumatic diseases and persistent aPL have reduced annexin A5 anticoagulant activity, whereas transient, nonpathogenic aPL have less effect on annexin A5 activity.

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