Hemophilia D factor (factor XII), red-cell deformability and platelet aggregates in raptors

In a spectrum of raptorial birds hemorrheologic factors were determined compared to normal human values. Significant findings were that Hageman factor (factor XII) levels were very low, the red-cell filteration rate was low, but the platelet-aggregate ratio was in the normal range. Relatively large, nucleated red cells appeared to be less flexible - deformable - than normal human red cells. Microvessel density (MVD) appeared to be in the normal range, but increased average capillary diameter may explain the lack of microvascular abnormalities. Hageman factor deficiency in raptors is comparable to human hemophilia D. However, the mechanisms of the lack of obvious thromboembolic and/or hemorrhagic phenomena may require further investigation.