Christmas factor

Who names this stuff, anyway?!

Coagulation factors, for the most part, have two names: a Roman numeral name and an English wordy name. Some of the wordy names, like accelerin, are descriptive and reasonable. Others, like Christmas factor, are colorful but not function-related. Here is a list of all the factors, with both names as well as their roles in coagulation.

I (fibrinogen) – forms the fibrin part of the clot
II (prothrombin) – serine protease
III (tissue factor) – inhibitor/cofactor
V (labile factor; accelerin) – cofactor
VII (proconvertin) – serine protease
VIII (antihemophilic factor) - cofactor
IX (Christmas factor) - serine protease
X (Stuart-Prower factor) - serine protease
XI (plasma thromboplastin antecedent) -  serine protease
XII (Hageman (contact) factor) – serine protease
XIII (fibrin stabilizing factor) – transglutaminase (cross-links fibrin in clot)
prekallikrein (Fletcher factor) - serine protease
HMWK (Fitzgerald factor) - cofactor

Factors I (fibrinogen) and II (thrombin) are generally referred to by their “name” names, where as factors V, VII, IX, X, XI, XII and XIII are referred to by their Roman numeral designation. Why, oh why, must coag be so complicated?