## **Core Concept**
The question tests understanding of red blood cell (RBC) membrane disorders. RBC membrane defects can be intrinsic (within the membrane itself) or extrinsic (related to external factors). Intrinsic defects involve abnormalities in the membrane proteins or lipids.

## **Why the Correct Answer is Right**
Hereditary spherocytosis (Option ) is a disorder characterized by an intrinsic defect in the RBC membrane. It results from mutations in genes encoding for proteins such as spectrin, ankyrin, band 3, and protein 4.2. These proteins are crucial for maintaining the structural integrity and flexibility of the RBC membrane. The defect leads to the production of spherocytes, which are sphere-shaped RBCs that are prematurely destroyed, resulting in hemolytic anemia.

## **Why Each Wrong Option is Incorrect**
* **Option A:** Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an enzyme deficiency that affects the RBC's ability to handle oxidative stress. It is not an intrinsic membrane defect but rather a metabolic disorder.
* **Option B:** Immune hemolytic anemia involves the destruction of RBCs due to antibodies against RBC antigens. This is an extrinsic cause, not an intrinsic membrane defect.
* **Option D:** Sickle cell disease results from a mutation in the hemoglobin gene, leading to abnormal hemoglobin (HbS) that causes RBCs to sickle under certain conditions. While it affects the RBC, it is not classified as a membrane defect but rather a hemoglobinopathy.

## **Clinical Pearl / High-Yield Fact**
A key clinical feature of hereditary spherocytosis is the presence of jaundice, splenomegaly, and often gallstones due to chronic hemolysis. A hallmark laboratory finding is the presence of spherocytes on the peripheral blood smear.

## **Correct Answer:** . Hereditary Spherocytosis