Factor VIII (F8) is a coagulation factor and member of the intrinsic pathway of the coagulation cascade. It is a cofactor for Factor IXa, which converts factor X to the activated form Xa. Defects in this gene result in hemophilia A, a recessive X-linked coagulation disorder, and high expression of Factor VIII is associated with greater risk for pulmonary embolism and deep vein thrombosis. In immunohistochemistry, it is expressed in the cytoplasm of endothelial cells and in extracellular deposits in tissues throughout the body. References: British Journal of Haematology. 2012. 157 (6): 653–63, PMID: 22530883; Invest Clin. 2016 Dec;57(4):377-87