**Core Concept**
The question is testing the understanding of bleeding disorders, particularly those that cause an elevated partial thromboplastin time (PTT). This is a critical concept in hematology, as it helps identify the underlying cause of bleeding and guides treatment decisions.

**Why the Correct Answer is Right**
Von Willebrand disease (VWD) is the most common inherited bleeding disorder, caused by a deficiency or dysfunction of von Willebrand factor (VWF). VWF is essential for platelet adhesion and stabilization of factor VIII in plasma. An abnormal PTT is a hallmark of VWD, as it reflects the impaired function of the intrinsic coagulation pathway. The correct answer is **Von-Willebrand disease** because it is the most common cause of an elevated PTT among the options listed.

**Why Each Wrong Option is Incorrect**
* **Option A:** Hemophilia A is caused by a deficiency of factor VIII, which affects the intrinsic coagulation pathway. However, Hemophilia A typically presents with an elevated PTT, but it's not the most common cause of an elevated PTT.
* **Option B:** Hemophilia B is caused by a deficiency of factor IX, which also affects the intrinsic coagulation pathway. Like Hemophilia A, it typically presents with an elevated PTT, but it's not the most common cause.
* **Option C:** Henoch-Schönlein purpura is a vasculitis that can present with bleeding manifestations, but it is not a primary bleeding disorder and does not typically cause an elevated PTT.
* **Option D:** Bernard-Soulier syndrome is a rare bleeding disorder caused by a deficiency of platelet glycoproteins, which affects platelet function. While it can cause bleeding, it is not typically associated with an elevated PTT.

**Clinical Pearl / High-Yield Fact**
Von Willebrand disease is often referred to as the "common bleeding disorder" because of its high prevalence and variable clinical presentation. It is essential to consider VWD in the differential diagnosis of bleeding disorders, especially in patients with a family history of bleeding or a personal history of easy bruising or bleeding.

**Correct Answer:** E. Von-Willebrand disease