Laboratory findings in Hemophilia B include which of the following?

Laboratory findings in Hemophilia B include which of the following?

• A. Decreased Factor IX and prolonged PTT
• B. Decreased Factor IX and prolonged PT
• C. Decreased Factor VIII and prolonged PTT
• D. Decreased Factor IX and normal PTT

Answer: (A)

Hemophilia B is caused by a deficiency of factor IX, which is part of the intrinsic coagulation pathway. The intrinsic pathway’s activity is reflected by the activated partial thromboplastin time (PTT), so a factor IX deficiency prolongs the PTT. The prothrombin time (PT) assesses the extrinsic pathway and remains normal because factor VII and the extrinsic pathway aren’t affected in hemophilia B. That’s why the typical lab picture is decreased factor IX with a prolonged PTT. A prolonged PT would point to an extrinsic issue, and a decreased factor VIII would indicate Hemophilia A, while a normal PTT would not align with an intrinsic pathway deficiency.

Hemophilia B is caused by a deficiency of factor IX, which is part of the intrinsic coagulation pathway. The intrinsic pathway’s activity is reflected by the activated partial thromboplastin time (PTT), so a factor IX deficiency prolongs the PTT. The prothrombin time (PT) assesses the extrinsic pathway and remains normal because factor VII and the extrinsic pathway aren’t affected in hemophilia B. That’s why the typical lab picture is decreased factor IX with a prolonged PTT. A prolonged PT would point to an extrinsic issue, and a decreased factor VIII would indicate Hemophilia A, while a normal PTT would not align with an intrinsic pathway deficiency.