Which is not a feature of paroxysmal nocturnal hemoglobinuria ?
**Core Concept**
Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired, life-threatening disease of the blood characterized by the destruction of red blood cells, bone marrow failure, and blood clot formation. The disease results from mutations in the PIGA gene, which codes for an enzyme essential for the synthesis of glycosylphosphatidylinositol (GPI), a lipid anchor that attaches proteins to cell membranes.
**Why the Correct Answer is Right**
PNH is characterized by the following features:
* Hemolytic anemia due to the destruction of red blood cells, which occurs due to the lack of GPI-anchored proteins on the surface of red blood cells, such as CD55 and CD59. These proteins normally protect red blood cells from complement-mediated lysis.
* Bone marrow failure, which can lead to aplastic anemia or leukemia.
* Thrombosis, which can occur due to the activation of the coagulation cascade and the formation of blood clots.
**Why Each Wrong Option is Incorrect**
**Option A:** Hemolytic anemia is a feature of PNH, making this option incorrect.
**Option B:** Bone marrow failure is also a feature of PNH, making this option incorrect.
**Option C:** Thrombosis is another feature of PNH, making this option incorrect.
**Clinical Pearl / High-Yield Fact**
PNH can be diagnosed using flow cytometry, which detects the absence of GPI-anchored proteins on the surface of blood cells. This is an important diagnostic tool, as PNH can mimic other diseases such as aplastic anemia or leukemia.
**Correct Answer:** D.