CCRN Neonatal Practice Test

Understanding the coagulation cascade and what each factor does helps explain why Hemophilia A is due to Factor VIII deficiency. Factor VIII serves as a crucial cofactor for Factor IXa in the intrinsic pathway, forming the tenase complex that converts Factor X to Xa. Without enough Factor VIII, thrombin generation drops and the clot formed is weaker, leading to spontaneous bleeding and prolonged bleeding after injury. This deficiency mainly shows up in laboratory testing as a prolonged activated partial thromboplastin time, while the prothrombin time remains normal because the extrinsic pathway is unaffected. Platelet function and platelet counts are typically normal in Hemophilia A, so bleeding patterns aren’t due to platelet problems. Hemophilia A is X-linked recessive, so it’s more common in males. A deficiency of Factor IX would cause a similar bleeding picture (Hemophilia B), whereas a deficiency of Factor VII would prolong the PT because it affects the extrinsic pathway. A practical clinical note: mild Hemophilia A can respond to desmopressin by releasing stored Factor VIII, while severe cases require Factor VIII replacement.