**Question:** Commonest presentation of sickle cell anemia is -

A. Painful crisis
B. Infections
C. Pulmonary hypertension
D. Gastrointestinal bleeding

**Core Concept:**

Sickle cell anemia is a genetic disorder caused by the inheritance of two mutated hemoglobin genes (HbS). When deoxygenated hemoglobin (HbS) polymerizes under low oxygen tension, red blood cells take an abnormal "sickle" shape, leading to hemolysis, reduced cell flexibility, and impaired blood flow. This results in organ damage, tissue ischemia, and various clinical presentations.

**Why the Correct Answer is Right:**

A. Painful crisis (Crise douloureuse) is the most common presentation of sickle cell anemia. Painful crisis occurs due to vaso-occlusion, where sickle red blood cells block blood vessels, leading to tissue ischemia and pain. This is why pain is the most common presentation, as it is triggered by deoxygenation, infection, dehydration, or other stressors.

**Why Each Wrong Option is Incorrect:**

B. Infections (Infections) are often associated with painful crises, but they are not the main cause of sickle cell anemia itself. Painful crisis is primarily triggered by the underlying hemoglobinopathy, not infections.

C. Pulmonary hypertension (Pulmonary hypertension) occurs in a minority of sickle cell patients and is a late complication. Painful crisis and acute chest syndrome are more common initial presentations.

D. Gastrointestinal bleeding (Gastrointestinal bleeding) is less common than painful crisis and acute chest syndrome. In severe cases, it may occur due to mucosal damage, but it is not the primary presentation of sickle cell anemia.

**Clinical Pearl:**

Understanding the pathophysiology of sickle cell anemia is crucial for proper diagnosis and management. Painful crisis is the primary presentation that should prompt a physician to suspect and investigate for sickle cell anemia. Infections, while often complicating the disease, are not the cause of the disease itself.