Antibodies against protein Z and fetal loss: current perspectives.

Protein Z (PZ) is a vitamin K-dependent plasma protein that serves as a cofactor for the inactivation of factor Xa. A number of investigators found low PZ levels in patients with haemorrhagic as well as thromboembolic diseases, although there is no clear evidence of a pathogenic link between PZ deficiency and these clinical disorders. Nevertheless, low PZ levels have been found in association with early fetal losses, especially those occurring before the 15th week of gestation and in patients with detectable antiphospholipid and anti-PZ antibodies. The current diagnostic relevance and therapeutic consequences of these parameters will be discussed.