Hemophilia B is due to deficiency of –
**Question:** Hemophilia B is due to deficiency of -
A. Factor VIII
B. Factor IX
C. Factor X
D. Factor XI
**Correct Answer:** B. Factor IX
**Core Concept:**
Hemophilia B is a hereditary bleeding disorder characterized by a deficiency in clotting factor IX, which is a key component of the intrinsic pathway of blood coagulation. The coagulation process involves multiple factors, including clotting factors, which are proteins that facilitate blood clotting.
**Why the Correct Answer is Right:**
Factor IX (also known as Christmas factor) is an essential enzyme that plays a crucial role in the intrinsic pathway of blood clotting. In the absence or reduced levels of Factor IX, the blood clotting process is impaired, leading to prolonged bleeding times and increased susceptibility to bleeding episodes, which is the clinical presentation of hemophilia B. The correct answer, Factor IX, is the deficient clotting factor in hemophilia B.
**Why Each Wrong Option is Incorrect:**
A. Factor VIII (Hemophilia A): Hemophilia A is caused by a deficiency in Factor VIII, which is involved in the common pathway of blood clotting. This is different from Hemophilia B, which is caused by a deficiency in Factor IX.
B. Factor X (Hemophilia C): Factor X deficiency is associated with Haemophilia C, also known as congenital Factor X deficiency, which is a distinct clinical entity from Hemophilia B.
C. Factor XI (Hemophilia D): Factor XI deficiency is linked to Hemophilia D, also known as Haemophilia D, which is a separate bleeding disorder from Hemophilia B.
D. Factor XI: As mentioned above, Factor XI deficiency is associated with Hemophilia D, not Hemophilia B.
**Clinical Pearl / High-Yield Fact:**
Hemophilia B is a rare genetic disorder that primarily affects males, who inherit the X-linked recessive gene from their mothers. Women, who are carriers of the defective gene, typically have no symptoms but can transmit the gene to their male offspring. This helps in understanding the inheritance pattern of hemophilia and its implications for genetic counseling.