Hemorrhagic Shock after Neonatal Circumcision: Severe Congenital Factor XIII Deficiency

Figure 1

Diagram of factor XIII activation and function. (a) Factor XIII is a protransglutaminase zymogen heterotetramer composed of two catalytic A subunits and two carrier B subunits. Thrombin cleaves the A subunits to make them catalytically active, followed by calcium-dependent dissociation of the B subunit to expose the active enzymatic site on the A subunit. (b) Activated factor XIIIa is then able to crosslink the fibrin strands, by catalyzing the formation of covalent bonds between glutamine and lysine residues on the fibrin a and g chains, resulting in a stable thrombus that is more resistant to degradation and less soluble.

(a)

(b)