Prothrombotic phenotype has been described in protein-Z deficient mice, but
the thrombotic risk associated with protein Z deficiency in human beings i
s 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 u
nknown.