**Question:** Most common symptom of Interstitial Lung disease is: March 2010

**Core Concept:** Interstitial lung diseases (ILDs) are a group of rare and heterogeneous conditions characterized by inflammation and fibrosis of the lung interstitium. Common symptoms include dyspnea, cough, and fatigue. The term "interstitial" refers to the affected structures within the lung tissue.

**Why the Correct Answer is Right:** The correct answer is "C. Fatigue" because fatigue is the most common symptom reported by patients with ILD. Fatigue can manifest as a persistent tiredness or exhaustion, often worsening with exertion or sleep, and is likely due to the underlying lung dysfunction.

**Why Each Wrong Option is Incorrect:**

A. **Dyspnea:** Although dyspnea is a common symptom in ILD, it is not the most common. Fatigue tends to be more predominant in patients with ILD.

B. **Cough:** Cough is a less common symptom compared to fatigue in ILD patients. ILD patients often present with non-productive cough, which means it does not involve producing sputum or phlegm.

D. **Chest Pain:** Chest pain is not the most common symptom in ILD. Fatigue is more likely to be the presenting complaint due to the underlying lung dysfunction.

**Clinical Pearl:** Fatigue in ILD can be attributed to several factors, including hypoxia, dyspnea, and decreased exercise tolerance. Proper evaluation and management of ILD involve excluding other causes of fatigue and assessing lung function tests, chest imaging, and pulmonary function tests (PFTs).

**Correct Answer:** C. Fatigue