In sickle cell anaemia true is –
**Core Concept**
Sickle cell anaemia is a genetic disorder caused by a mutation in the HBB gene, leading to the production of abnormal haemoglobin (HbS) that causes red blood cells to become misshapen and sickle-shaped. This abnormal shape causes the cells to be more rigid and prone to sticking together, leading to vaso-occlusion and tissue damage.
**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of sickle cell anaemia, specifically the role of deoxyhaemoglobin in causing polymerization of haemoglobin S. When red blood cells are deoxygenated, the abnormal haemoglobin molecules stick together, forming long chains that cause the cell membrane to buckle and create the characteristic sickle shape. This process is reversible when the cells are oxygenated, but repeated episodes of vaso-occlusion and tissue damage can lead to chronic complications such as organ failure and increased risk of infections.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the pathophysiology of sickle cell anaemia. While oxidative stress may play a role in the disease, it is not the primary cause of the abnormal haemoglobin polymerization.
* **Option B:** This option is incorrect because it is a general statement about the function of haemoglobin, rather than a specific characteristic of sickle cell anaemia. Haemoglobin is responsible for transporting oxygen to tissues, but the abnormal shape of red blood cells in sickle cell anaemia is a result of the specific mutation in the HBB gene.
* **Option C:** This option is incorrect because it is a treatment for sickle cell anaemia, rather than a characteristic of the disease. Hydroxyurea is a medication that can help increase fetal haemoglobin production, reducing the severity of the disease.
**Clinical Pearl / High-Yield Fact**
Sickle cell anaemia is a classic example of a genetic disorder that can be diagnosed through newborn screening, and early detection can significantly improve patient outcomes. It is essential for healthcare providers to be aware of the signs and symptoms of sickle cell anaemia, including episodes of pain crisis, anemia, and increased risk of infections.
**Correct Answer: D.**