What condition would be suspected if a patient has no bleeding complications but shows a prolonged APTT?

A prolonged Activated Partial Thromboplastin Time (APTT) indicates a defect in the intrinsic and common pathways of coagulation. In this scenario, the presence of prolonged APTT without bleeding complications suggests a deficiency in a coagulation factor that may not necessarily cause bleeding symptoms, depending on the degree of the deficiency and the presence of compensatory mechanisms in the patient.

Factor XI deficiency is associated with a prolonged APTT but typically shows minimal to no bleeding complications, particularly compared to deficiencies of more severe factors like Factor VIII or Factor X, which are more directly involved in the bleeding process. In fact, many individuals with Factor XI deficiency remain asymptomatic, especially those with mild deficiencies.

Other conditions listed involve factors that are more commonly associated with significant bleeding issues. For instance, Factor VIII deficiency often leads to hemophilia A, which is characterized by bleeding tendencies. Similarly, deficiencies in Factor VII may lead to bleeding, particularly given its role in the extrinsic pathway. Prothrombin deficiency could also lead to bleeding complications, as prothrombin is essential for normal clot formation.

Thus, given that a patient exhibits a prolonged APTT but no bleeding complications, it is most consistent with Factor XI deficiency, making it the most appropriate