Okay, let's tackle this question about sickle cell disease. The question is asking which statement is false. First, I need to recall the key points about sickle cell disease.

Sickle cell disease is an autosomal recessive disorder caused by a mutation in the beta-globin gene. The main issue is the production of abnormal hemoglobin, called hemoglobin S. When oxygen levels are low, the red blood cells become sickle-shaped, leading to various complications like anemia, pain crises, and organ damage.

Now, the question is asking for the exception. Let me think about common misconceptions or incorrect statements about this condition. For example, some people might confuse it with thalassemia, which is another hemoglobinopathy. Or maybe a statement about treatment. Let's consider possible options.

If one of the options says it's caused by a defect in alpha-globin, that would be wrong because sickle cell is beta-globin. If an option claims it's autosomal dominant, that's incorrect. Another possible false statement could be that it's a disorder of white blood cells instead of red blood cells. Also, maybe a treatment-related error, like using hydroxyurea for something else.

I need to structure the explanation with the core concept first, then explain why the correct answer is right, address each wrong option, and end with a clinical pearl. Let's make sure each section is concise and covers the necessary points without going over character limits.

**Core Concept** Sickle cell disease (SCD) is an autosomal recessive hemoglobinopathy caused by a mutation in the **β-globin gene (HBB)**, leading to abnormal hemoglobin S (HbS). The hallmark is **deformed RBCs** under hypoxia, causing vaso-occlusive crises, hemolytic anemia, and end-organ damage.

**Why the Correct Answer is Right** The false statement is **Option D: "Sickle cell disease is associated with increased RBC flexibility under hypoxic conditions."** HbS polymerization under hypoxia causes RBCs to become rigid, sickle-shaped, and prone to hemolysis. This rigidity leads to microvascular occlusion and tissue ischemia, not increased flexibility.

**Why Each Wrong Option is Incorrect**
**Option A:** "SCD is inherited in an autosomal recessive pattern" is correct. Two defective β-globin alleles are required for the disease.
**Option B:** "Hydroxyurea is a first-line therapy to reduce vaso-occlusive crises" is correct. It increases fetal hemoglobin (HbF) production, inhibiting HbS polymerization.
**Option C:** "Chronic hemolysis and extravascular hemolysis in the spleen are characteristic" is correct. Sickle RBCs are removed in the spleen, causing anemia and jaundice.

**Clinical Pearl / High-Yield Fact** Remember the **"Sickledex" test** for screening, but confirm with **HPLC or electrophoresis**. Never confuse SCD with **β-thalassemia**—both cause microcytic anemia, but β-thalassemia lacks the vaso-occlusive crises seen in SCD.

**Correct Answer: D. Sickle cell disease is associated with increased

✓ Correct Answer: C. Sticky patch' is generated as a result of replacement of a non polar residue with a polar residue