Bleeding disorders with ↑ APTT and ↑PT:a) Factor 13 deficiencyb) Severe liver diseasec) Immune thrombocytopenic purpurad) Leiden (Factor V) deficiency

**Core Concept**
Bleeding disorders involving coagulation factor deficiencies or dysfunction can be identified by abnormal prothrombin time (PT) and activated partial thromboplastin time (APTT) results. In this scenario, both PT and APTT are prolonged, indicating a problem in the coagulation cascade.

**Why the Correct Answer is Right**
The correct answer is Factor 13 deficiency (Option A). Factor 13 is a transamidating enzyme that stabilizes fibrin clots. Deficiency in Factor 13 leads to impaired clot stabilization, resulting in prolonged APTT and PT. This is because Factor 13 is involved in the intrinsic and common pathways of coagulation, affecting both PT and APTT.

**Why Each Wrong Option is Incorrect**
**Option B:** Severe liver disease can affect both PT and APTT, but it typically causes a prolongation of PT more than APTT due to decreased production of coagulation factors in the liver. However, it is not the best choice in this scenario where both PT and APTT are equally prolonged.

**Option C:** Immune thrombocytopenic purpura (ITP) is a bleeding disorder characterized by thrombocytopenia (low platelet count), which affects primary hemostasis rather than the coagulation cascade. It would not typically affect PT or APTT.

**Option D:** Leiden (Factor V) deficiency is a rare condition that affects Factor V, a crucial component of the coagulation cascade. However, it primarily affects PT and not APTT, as Factor V is involved in the extrinsic pathway of coagulation.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with a bleeding disorder, it's essential to consider the specific coagulation pathway affected. A prolonged APTT with a normal PT may indicate a problem with the intrinsic or common pathways, while a prolonged PT with a normal APTT may suggest a problem with the extrinsic pathway.

**Correct Answer:** A. Factor 13 deficiency