title: Prevalence of annexin A5 resistance in children and adolescents with rheumatic diseases.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Children's Hospital at Montefiore, Department of Pediatrics, Division of Rheumatology, Bronx, NY 10467, USA. dwahezi@montefiore.org
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Wahezi
authors.forename: Norman T
authors.initials: NT
authors.lastname: Ilowite
authors.forename: Swapnil
authors.initials: S
authors.lastname: Rajpathak
authors.forename: Jacob H
authors.initials: JH
authors.lastname: Rand
mesh_terms: D000293:Adolescent; D017304:Annexin A5 / Q000097:blood*; D017152:Antibodies, Antiphospholipid / Q000097:blood; D016736:Antiphospholipid Syndrome / Q000097:blood / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000453:epidemiology*; D008297:Male; D008947:Mixed Connective Tissue Disease / Q000097:blood / Q000453:epidemiology; D015995:Prevalence; D012216:Rheumatic Diseases / Q000097:blood / Q000453:epidemiology*; D013927:Thrombosis / Q000097:blood / Q000453:epidemiology; D055815:Young Adult
chemical_list: D017304:Annexin A5; D017152:Antibodies, Antiphospholipid