Plasma protein Z levels in healthy and high-risk newborn infants

Plasma protein Z and protein C inhibitors and their role in hypercoagulability of thalassemia

A hypercoagulable state has been described in thalassemia patients, partly due to a deficiency of inhibitors, protein C (PC) in particular. Since a potential role of a new hemostatic factor named protein Z (PZ) has been reported in hypercoagulability, we evaluated plasma PZ and PC levels in thalassemia and their possible relation to the hypercoagulable state. Sixty subjects with thalassemia major and 10 with thalassemia intermedia (TI) followed at our Department were enrolled in the study. An age-matched control group of healthy subjects was considered. PZ, thrombin-antithrombin complexes, PC concentration (PC:Ag) and activity (PC:Act) were measured. PZ, PC:Ag and PC:Act were significantly lower in thalassemia major and thalassemia intermedia subjects than in 30 healthy controls (p < 0.001), while thrombin-antithrombin complex levels were significantly increased (p < 0.001) and related to PC levels but not to PZ levels (p < 0.05). PZ and PC levels are reduced in thalassemia but only PC has an effect on the thalassemia hypercoagulable state.

[Protein Z: a new factor of thrombophilia?]

INTRODUCTION

Sometimes, in front of a clinical setting of thrombophilia, the biological findings are helpless. Therefore we suggest to test a protein Z deficiency.

EXEGESIS

Protein Z is a vitamin-K dependent protein forming a complex with the Z protein-dependent protease inhibitor for inhibiting the activated factor X; so protein Z acts as a "natural low molecular weight heparin". The prothrombotic phenotype associated with protein Z deficiency includes early fetal losses (before the 20th week of gestation), early and relapsing venous thrombosis in patients with factor V Leiden mutation and somehow ischaemic stroke in young people.

CONCLUSION

The protein Z deficiency seems to be associated with a particular prothrombotic phenotype including early fetal losses as well as early and relapsing venous thromboses in patients carrying the factor V Leiden mutation. It is unclear whether or not it plays a role as a thrombophilic factor especially in the arterial vascular field.