Passovoy factor: A hitherto unrecognised factor necessary for haemostasis.

Abstract A moderate bleeding diathesis transmitted as an autosomal dominant was found in five members of four generations of the same family. The affected patients had prolonged partial thromboplastin-times and normal levels of all the known clotting-factors. The haemorrhagic diathesis was attributed to a deficiency of a hitherto unrecognised coagulation factor—i.e., the Passovoy factor.