Most common feature of sarcoidosis on chest X-ray is:March 2011, March 2013
**Core Concept**
Sarcoidosis is a systemic granulomatous disease characterized by the formation of non-caseating granulomas in various organs, including the lungs. The chest X-ray is a key diagnostic tool in identifying pulmonary involvement.
**Why the Correct Answer is Right**
The most common feature of sarcoidosis on chest X-ray is the bilateral hilar lymphadenopathy, which is thought to be due to the accumulation of immune cells, such as T lymphocytes and macrophages, in the lymph nodes. This is a result of the body's immune response to the formation of granulomas in the lungs. The lymph nodes become enlarged and can cause the hilar regions to appear widened on the chest X-ray.
**Why Each Wrong Option is Incorrect**
**Option A:** Upper lobe fibrosis is not a characteristic feature of sarcoidosis, which typically presents with bilateral hilar lymphadenopathy.
**Option B:** Pulmonary infiltrates can be seen in sarcoidosis, but they are not the most common feature on chest X-ray.
**Option C:** Pleural effusion is not typically associated with sarcoidosis, which usually presents with lymphadenopathy and pulmonary infiltrates.
**Clinical Pearl / High-Yield Fact**
Bilateral hilar lymphadenopathy is a classic radiographic finding in sarcoidosis, and its presence should prompt further investigation, including pulmonary function tests and a high-resolution CT scan of the chest.
**Correct Answer:** A. Bilateral hilar lymphadenopathy