**Question:** True about sarcoidosis is-

A. It is a granulomatous inflammation of unknown cause
B. It primarily affects the lungs and skin
C. It is caused by an infection with Propionibacterium acnes
D. It is a neoplastic disorder

**Core Concept:**
Sarcoidosis is a multisystem granulomatous inflammation of unknown cause, characterized by the formation of non-caseating granulomas in various organs. Granulomas are collections of macrophages and lymphocytes that form in response to foreign substances, infections, or unknown triggers. In sarcoidosis, the immune system overreacts, leading to the formation of these granulomas.

**Why the Correct Answer is Right:**
Sarcoidosis is indeed a granulomatous inflammation, which means it involves the formation of non-caseating granulomas in various organs. In the context of this question, sarcoidosis is a correct answer because it is a granulomatous inflammation, not a neoplastic (cancer) disorder.

**Why Each Wrong Option is Incorrect:**
A. Sarcoidosis is a granulomatous inflammation, but it is not caused by an infection with Propionibacterium acnes. This bacterium is involved in acne, not sarcoidosis.
B. Sarcoidosis primarily affects the lungs and skin, which is partially correct but does not encompass the full range of organs involved. The disease can involve multiple organs, including the lungs, skin, lymph nodes, eyes, heart, joints, liver, kidneys, and central nervous system.
C. Sarcoidosis is not a neoplastic disorder (cancer), so this option is incorrect.

**Clinical Pearl:**
Sarcoidosis is a complex, multi-factorial disorder involving genetic, environmental, and immunological factors. The exact cause remains unknown, but it is believed to be triggered by a combination of genetic predisposition, environmental factors, and immune dysregulation. The involvement of multiple organs, the non-caseating granulomas, and the unique clinical presentation differentiate sarcoidosis from tuberculosis or other granulomatous diseases.

For example, sarcoidosis presents with a characteristic skin rash, Lungs: hilar lymphadenopathy and pulmonary infiltrates, and Eyes: anterior uveitis. Awareness of these clinical features can aid in making the correct diagnosis and prompt appropriate management.

**Correct Answer:**
The correct answer is B, which states that sarcoidosis primarily affects the lungs and skin. However, the question asks for a true statement about sarcoidosis, not just its primary sites of involvement. Therefore, the correct answer is:

**Correct Answer:** True about sarcoidosis is that it is a multisystem granulomatous disease with a complex etiology involving genetic and environmental factors, leading to immune dysregulation and the formation of non-caseating granulomas in various organs.