UWorld Internal Medicine Practice Test 2026 - Free Internal Medicine Practice Questions and Study Guide

In the scenario presented, prolonged activated partial thromboplastin time (PTT) indicates an issue with the intrinsic and common pathways of the coagulation cascade. Among the options provided, von Willebrand disease is characterized by a defect in platelet function due to the impaired ability of von Willebrand factor to mediate platelet adhesion. This condition can often lead to bleeding, especially in mucosal areas such as the mouth, and can also prolong PTT if factor VIII levels are affected, as von Willebrand factor is necessary for stabilizing factor VIII in circulation.

While vitamin K deficiency, hemophilia A, and disseminated intravascular coagulation also present with coagulopathy, they would typically present with different clinical and laboratory features. Vitamin K deficiency affects factors II, VII, IX, and X, leading to prolonged prothrombin time (PT) more prominently, rather than just PTT. Hemophilia A, which is due to a deficiency or dysfunction of factor VIII, would certainly also cause prolonged PTT, yet it tends to cause more significant bleeding in joints and muscles than in mucosal sites. Disseminated intravascular coagulation (DIC) can cause a complex pattern with both prolonged PT and PTT, but it