Commonest presentation of sickle cell anemia –
**Core Concept**
Sickle cell anemia is a genetic disorder caused by a mutation in the HBB gene, leading to the production of abnormal hemoglobin (hemoglobin S). This abnormal hemoglobin causes red blood cells to become misshapen and rigid, resulting in a variety of clinical manifestations.
**Why the Correct Answer is Right**
The commonest presentation of sickle cell anemia is typically in early childhood, often after a viral illness, which triggers a sickling crisis. This is due to the increased concentration of hemoglobin S in deoxygenated red blood cells, leading to vaso-occlusion and ischemia. The resulting acute pain crisis is the hallmark presentation of sickle cell anemia, often involving the bones, joints, and abdomen.
**Why Each Wrong Option is Incorrect**
**Option A:** While splenomegaly is a common feature in early childhood due to sequestration of sickled red blood cells, it is not the commonest presentation.
**Option B:** jaundice is not a characteristic presentation of sickle cell anemia, as the disorder primarily affects hemoglobin, not bilirubin metabolism.
**Option C:** Anemia is a feature of sickle cell disease, but it is not the most common presentation, as many patients have a relatively normal hemoglobin level between crises.
**Clinical Pearl / High-Yield Fact**
The classic "sickle cell crisis" is often precipitated by a viral infection, which triggers a cascade of events leading to vaso-occlusion and ischemia.
**Correct Answer: A. Acute pain crisis.**