## **Core Concept**
Hemophilia A, also known as classic hemophilia, is a genetic disorder caused by missing or defective **Factor VIII**, a clotting factor necessary for blood coagulation. The severity of hemophilia A is classified based on the level of Factor VIII activity in the blood, with severe hemophilia A typically having Factor VIII levels less than 1%, moderate hemophilia A between 1-40%, and mild hemophilia A between 41-50% of normal activity.

## **Why the Correct Answer is Right**
The patient's presentation of recurrent bleeding into joints during contact sports, without spontaneous bleeding, and a family history of similar problems, is consistent with mild hemophilia A. Mild hemophilia A is characterized by **Factor VIII levels between 41-50%** of normal. This condition leads to a reduced but not completely absent ability to form blood clots, resulting in bleeding primarily under conditions of trauma or surgery, but not spontaneously.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option does not specify a factor level consistent with mild hemophilia A.
- **Option B:** This option suggests a level that might be considered moderate or severe, depending on the exact percentage provided, but it does not align with the definition of mild hemophilia A.
- **Option C:** Levels less than 1% are indicative of severe hemophilia A, which does not match the patient's mild condition.
- **Option D:** While not explicitly provided, if option D mentions a Factor VIII level around 45% or another value within the 41-50% range, it would be correct; otherwise, it's incorrect based on the information given.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the severity of hemophilia A correlates with the risk of spontaneous bleeding: patients with **severe hemophilia A (<1% Factor VIII activity)** experience frequent spontaneous bleeds, those with **moderate hemophilia A (1-40% activity)** may bleed with minor trauma, and those with **mild hemophilia A (41-50% activity)** typically only bleed with significant trauma or surgery. ## **Correct Answer:** D. 40-50%