True about Haemophilia A are all except
**Core Concept**
Haemophilia A is a genetic disorder caused by a deficiency of factor VIII, a crucial protein in the blood clotting cascade. This deficiency leads to excessive bleeding, particularly in joints and muscles, due to impaired platelet function and clot formation. Factor VIII is a vitamin K-dependent coagulation factor that plays a key role in the intrinsic pathway of blood coagulation.
**Why the Correct Answer is Right**
The correct answer will be incorrect regarding Haemophilia A. Factor VIII is produced in the liver and is essential for the activation of factor X by factor IX in the intrinsic pathway of blood coagulation. A deficiency of factor VIII leads to prolonged bleeding time and increased susceptibility to bleeding.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Haemophilia A is not caused by a deficiency of factor IX, which is associated with Haemophilia B. Factor IX is a different vitamin K-dependent coagulation factor that plays a key role in the intrinsic pathway of blood coagulation.
**Option B:** This option is incorrect because Haemophilia A is not caused by a deficiency of platelets. Platelets are involved in the formation of a platelet plug at the site of injury, but a deficiency of platelets is associated with thrombocytopenia, not Haemophilia A.
**Option C:** This option is incorrect because Haemophilia A is not caused by a deficiency of vitamin K. Vitamin K is necessary for the production of several coagulation factors, including factors II, VII, IX, and X, but Haemophilia A is specifically caused by a deficiency of factor VIII.
**Option D:** This option is incorrect because Haemophilia A is not caused by a deficiency of fibrinogen. Fibrinogen is a protein that is converted to fibrin, which forms the clot, but a deficiency of fibrinogen is associated with hypofibrinogenemia, not Haemophilia A.
**Clinical Pearl / High-Yield Fact**
Haemophilia A is an X-linked recessive disorder, which means that it primarily affects males, who have only one X chromosome. Females can be carriers of the disease, but they are usually asymptomatic or mildly affected.
**Correct Answer:**