Protein Z levels and central retinal vein or artery occlusion.
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.
Koren-Michowitz
Maya
M
Department of Hematology, Assaf Harofeh Medical Center, Zeriffin, Israel. mayakoren@asaf.health.gov.il
Eting
Eva
E
Rahimi-Levene
Naomi
N
Garach-Jehoshua
Osnat
O
Volcheck
Yulia
Y
Kornberg
Abraham
A
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
D001798:Blood Proteins; C026080:plasma protein Z