Protein Z is a
vitamin-K-dependent plasma
glycoprotein; its physiological function is not clear. Low
protein Z levels were found in patients with otherwise unexplained
bleeding disorders. It was therefore suggested that low
protein Z levels might be associated with a
bleeding diathesis. In the present study we measured
protein Z levels in plasma samples of 48 patients with a suspected
bleeding disorder and in plasma samples of 200 healthy adult individuals. We found
protein Z to have a wide normal range in healthy men and women. Significantly lower
protein Z levels were observed in women compared to men, whereas no correlation was found with age or other
vitamin-K-dependent coagulation
proteins. None of the 48 patients with a
bleeding disorder had a
protein Z level below the normal range. However,
protein Z was significantly lower in the group of male patients with a
bleeding history as compared to healthy men. In conclusion, our data indicate that low-normal
protein Z levels are not associated with a
bleeding tendency. However, it remains to be determined whether a low
protein Z level is a weak cofactor associated with an increased
bleeding tendency and whether decreased or absent
protein Z (conditions not detected in our patients) might constitute a haemorrhagic
diathesis.