A 15–year–old female presented to the emergency department with history of recurrent epistaxis, hematuria and hematochezia. There was a history of profuse bleeding from the umbilicus stump at birth. Previous investigations revealed normal prothrombin time, activated partial thromboplastin time, thrombin time and fibrinogen levels. Her platelet counts as well as platelet function tests were normal but urea clot lysis test was positive. Which one of the following clotting factor is most likely to be deficient –

**Core Concept**
The patient's presentation of recurrent bleeding from multiple sites, including mucocutaneous and gastrointestinal, suggests a coagulation disorder. The normal platelet count and function tests indicate that the bleeding is not due to a platelet disorder, but rather a problem with the coagulation cascade. The urea clot lysis test being positive suggests that the body is able to dissolve clots, which is a hallmark of fibrinolysis.

**Why the Correct Answer is Right**
The patient's symptoms and positive urea clot lysis test are suggestive of a deficiency in a clotting factor that is involved in the regulation of fibrinolysis. The correct answer, **Factor XIII**, is a clotting factor that plays a crucial role in stabilizing blood clots by cross-linking fibrin molecules. A deficiency in Factor XIII would lead to a tendency for blood clots to break down, resulting in excessive bleeding.

**Why Each Wrong Option is Incorrect**
* **Option A:** Factor VIII is a clotting factor involved in the intrinsic pathway of coagulation. A deficiency in Factor VIII leads to hemophilia A, which is characterized by excessive bleeding into joints and muscles, not mucocutaneous bleeding.
* **Option B:** Factor XI is a clotting factor involved in the intrinsic pathway of coagulation. A deficiency in Factor XI leads to a mild bleeding disorder, but it is not typically associated with mucocutaneous bleeding or a positive urea clot lysis test.
* **Option C:** Factor X is a clotting factor involved in both the intrinsic and extrinsic pathways of coagulation. A deficiency in Factor X leads to a more severe bleeding disorder, but it is not typically associated with mucocutaneous bleeding or a positive urea clot lysis test.

**Clinical Pearl / High-Yield Fact**
Factor XIII deficiency is a rare bleeding disorder that can be diagnosed by a specific bleeding time test or by genetic testing. It is essential to consider this diagnosis in patients with recurrent mucocutaneous bleeding and a positive urea clot lysis test.

**Correct Answer:** D. Factor XIII. Factor XIII deficiency.

✓ Correct Answer: D. Factor XIII