title: Antiphospholipid antibodies and platelet activation as risk factors for thrombosis in thrombocythaemia.
abstract: BACKGROUND
  Risk factors for thrombosis (TB) in thrombocythaemia (TC) associated with myeloproliferative disorder (MPD) are not well defined.
  
  
  METHODS
  We measured antiphospholipid antibodies (APLA) in 35 patients with TC associated with MPD. Fourteen had TB and 21 did not. We assayed IgG and IgM APLA by ELISA for 6 antigens: beta2GP1, cardiolipin (CL), phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylethanolamine (PE) and FVII/VIIa, together with markers of activation of platelets (CD62P) and endothelium [endothelial microparticles (EMP)].
  
  
  RESULTS
  At least one positive APLA was detected in 66% of TC patients overall. The incidence was significantly higher in the TB subgroup (92.8%) than non-TB (47.6%, p < 0.05). Multiple APLA (positive for more than one antigen) were also more frequent in TB, for both IgG and IgM, for all 6 antigens tested (p < 0.05). However, IgM APLA predominated, being about 2-fold more frequently positive than IgG for all 6 antigens. Platelet CD62P was significantly higher in the TB group (p < 0.05). EMP did not differ between TB and non-TB. The most frequent thrombotic complication was recurring ischemic cerebral vascular accidents (ICVA), leading to progressive cognitive impairment. Venous TB often developed at unusual sites. Recurring and reversible TB were common features in TC.
  
  
  CONCLUSIONS
  This study suggests that APLA and platelet activation are risk factors for TB in TC. APLA are prevalent in TC, and IgM APLA predominated over IgG. Activation of platelets but not of endothelium may be consistent with the reversible and recurrent features of TB in TC.
authors.affiliation: Wallace H Coulter Platelet Laboratory, Division of Hematology/Oncology, University of Miami School of Medicine, Miami, FL, 33136, USA.
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Bidot
authors.forename: Wenche
authors.initials: W
authors.lastname: Jy
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Horstman
authors.forename: Eugene R
authors.initials: ER
authors.lastname: Ahn
authors.forename: Loreta
authors.initials: L
authors.lastname: Bidot
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Fontana
authors.forename: Yeon S
authors.initials: YS
authors.lastname: Ahn
mesh_terms: D000328:Adult; D000368:Aged; D017152:Antibodies, Antiphospholipid / Q000276:immunology*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D008875:Middle Aged; D015539:Platelet Activation; D012307:Risk Factors; D013922:Thrombocytosis / Q000097:blood* / Q000150:complications / Q000276:immunology*; D013927:Thrombosis / Q000097:blood* / Q000150:complications / Q000276:immunology*
chemical_list: D017152:Antibodies, Antiphospholipid; D007074:Immunoglobulin G