Commonest presentation of sickle cell anaemia 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). This abnormal haemoglobin polymerizes under low oxygen conditions, causing red blood cells to assume a sickle shape and leading to various clinical manifestations.
**Why the Correct Answer is Right**
The commonest presentation of sickle cell anaemia is an episode of acute pain, often referred to as a 'crisis'. This occurs due to the sickling of red blood cells, which can cause vaso-occlusion and tissue ischemia, leading to pain in the bones, joints, and other areas. The pain is usually severe and can be accompanied by other symptoms such as fever, jaundice, and pallor.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because although infection is a common complication of sickle cell anaemia, it is not the most common presentation of the disease.
* **Option B:** This option is incorrect because although anaemia is a hallmark of sickle cell anaemia, it is not the most common presentation of the disease.
* **Option C:** This option is incorrect because although splenomegaly can occur in sickle cell anaemia, it is not the most common presentation of the disease.
**Clinical Pearl / High-Yield Fact**
It's essential to note that sickle cell anaemia can present at any age, but the first episode of pain crisis usually occurs in childhood or adolescence.
**Correct Answer: D. Acute pain crisis**