title: Protein Z levels and central retinal vein or artery occlusion.
abstract: OBJECTIVE
  Central retinal vein occlusion (CRVO) and central retinal artery occlusion (CRAO) are common disorders associated with risk factors for atherosclerosis. Protein Z is a cofactor for the inactivation of activated factor X (Xa) by the protein Z dependent protease inhibitor. Protein Z deficiency was recently linked to increased risk of arterial thrombosis. We investigated whether CRVO and CRAO are associated with low protein Z levels.
  
  
  METHODS
  Patients with CRVO, CRAO or recurrent branch retinal vein occlusion were recruited to the study. Protein Z level, lupus anticoagulant (LAC), anticardiolipin antibodies (ACA) and activated protein C resistance (APCR) were determined in plasma from patients (n = 36) and healthy controls (n = 42).
  
  
  RESULTS
  Thirty patients in the study group had traditional risk factors for retinal vessel occlusion and six patients had none. There was no significant difference in protein Z levels between the whole study group patients and controls (1995 +/- 810 vs. 2010 +/- 603 ng/mL, P = 0.922). However, patients with no risk factors for retinal vessel occlusion had significantly lower protein Z levels than controls (1379 +/- 682 vs. 2010 +/- 603 ng/mL, P = 0.022). Positive LAC was found in six patients and one control subject (P = 0.04). There were three patients and one control subject with abnormal APCR (P = 0.3) and none with positive ACA. Low protein Z level (lower than fifth percentile of control) was not associated with the presence of LAC or APCR.
  
  
  CONCLUSIONS
  Low protein Z level may be another risk factor for retinal vessel occlusion in patients without traditional risk factors for these disorders.
authors.affiliation: Department of Hematology, Assaf Harofeh Medical Center, Zeriffin, Israel. mayakoren@asaf.health.gov.il
authors.forename: Maya
authors.initials: M
authors.lastname: Koren-Michowitz
authors.forename: Eva
authors.initials: E
authors.lastname: Eting
authors.forename: Naomi
authors.initials: N
authors.lastname: Rahimi-Levene
authors.forename: Osnat
authors.initials: O
authors.lastname: Garach-Jehoshua
authors.forename: Yulia
authors.initials: Y
authors.lastname: Volcheck
authors.forename: Abraham
authors.initials: A
authors.lastname: Kornberg
mesh_terms: D000328:Adult; D000368:Aged; D001798:Blood Proteins / Q000032:analysis* / Q000172:deficiency; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015356:Retinal Artery Occlusion / Q000097:blood* / Q000209:etiology; D012170:Retinal Vein Occlusion / Q000097:blood* / Q000209:etiology; D012307:Risk Factors
chemical_list: D001798:Blood Proteins; C026080:plasma protein Z