## **Core Concept**
Hemophilia A, also known as classic hemophilia, is a genetic disorder caused by missing or defective **factor VIII**, a crucial protein for blood clotting. This condition leads to prolonged bleeding, particularly into joints and muscles. Laboratory findings are essential for diagnosing and managing the condition.

## **Why the Correct Answer is Right**
The correct answer, , shows that in hemophilia A, the **partial thromboplastin time (PTT)** or **activated partial thromboplastin time (aPTT)** is prolonged. This is because factor VIII is part of the intrinsic pathway of blood coagulation, which aPTT measures. The **prothrombin time (PT)** remains normal since factor VIII is not involved in the extrinsic pathway, measured by PT. The **bleeding time** is usually normal as it reflects platelet function, not coagulation factors. The **platelet count** is also normal because hemophilia A does not affect platelet numbers.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests that both PT and aPTT are prolonged. However, in hemophilia A, only aPTT is prolonged because the defect is in the intrinsic pathway, not affecting PT.
- **Option B:** This option indicates that bleeding time is prolonged, which is incorrect because bleeding time primarily reflects platelet function, and hemophilia A is a coagulation disorder, not a platelet disorder.
- **Option D:** This option states that the platelet count is decreased, which is incorrect because hemophilia A does not affect the number of platelets; it affects the function of a specific clotting factor (factor VIII).

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that hemophilia A can be treated with **desmopressin** (for mild cases) or **factor VIII concentrates**. Desmopressin works by stimulating the release of factor VIII from storage sites into the bloodstream. Knowing the specific lab findings helps in quickly identifying and managing the condition.

## **Correct Answer:** . Prolonged aPTT with normal PT, bleeding time, and platelet count.