Mutations are from database15 and if marked by an asterisk, from Table 2. Factor VIII was determined in patient plasma as clotting activity (VIII:C) or total antigen (Ag) with bold for dysfunctional (excess) antigen; “?” indicates value not reported.15 Inh, high titer inhibitor in at least one patient; β, beta strand (numbered) with loops numbered following strands. Factor VIII, homologous residues in h, human; m, murine; p, porcine; c, canine. Factor V, homologous residues in h, human; m, murine; b, bovine (see Figure 1 for sequence references).