## **Core Concept**
The question tests understanding of Interstitial Lung Diseases (ILDs) and their effects on pulmonary function tests, specifically the pattern of lung function impairment. ILDs are primarily known for causing restrictive lung diseases, but some can present with an obstructive pattern.

## **Why the Correct Answer is Right**
Sarcoidosis is a systemic granulomatous disease that can affect the lungs and is known to cause a variety of pulmonary function test abnormalities, including both restrictive and obstructive patterns. The disease can lead to inflammation and granuloma formation in the airways, causing obstruction. Therefore, among the given options, sarcoidosis can indeed present with an obstructive pattern.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Usual Interstitial Pneumonia (UIP) is typically associated with a restrictive pattern on pulmonary function tests, not an obstructive one. UIP is characterized by inflammation and fibrosis of the lung parenchyma.
- **Option B:** Lymphangitic Carcinomatosis usually presents with a restrictive pattern due to the infiltration of cancer cells into the lymphatic vessels of the lung, leading to fibrosis and stiffness.
- **Option D:** Idiopathic Pulmonary Fibrosis (IPF) is a classic example of a restrictive lung disease. It leads to fibrosis of the lung parenchyma, resulting in decreased lung volumes and capacities.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while ILDs are predominantly associated with restrictive lung disease, certain conditions like sarcoidosis can cause airway involvement leading to an obstructive pattern. This highlights the importance of considering ILDs in the differential diagnosis of obstructive lung diseases as well.

## **Correct Answer:** C. Sarcoidosis