Frequency of protein Z deficiency in patients with ischaemic stroke.

Prothrombotic phenotype has been described in protein-Z deficient mice, but the thrombotic risk associated with protein Z deficiency in human beings is unknown. We saw a protein Z plasma concentration deficiency of about 20% in 169 patients, from two hospitals, who had ischaemic stroke, whereas the frequency in 88 controls was about 5%. We saw no increase in the frequency of protein Z deficiency in 56 patients with venous thrombophilia. However, why protein Z deficiency was only observed in arterial thrombosis remains unknown.