**Question:** Garland sign on CXR in sarcoidosis involves all except:-

A. Centrilobular nodules
B. Interlobular septal thickening
C. Pleural effusion
D. Lung fibrosis

**Core Concept:**
The Garland sign is a radiological feature observed on chest X-ray (CXR) in patients with sarcoidosis, a multi-system granulomatous inflammatory disease. Sarcoidosis typically presents with various radiological findings, including centrilobular nodules, interlobular septal thickening, pleural effusion, and lung fibrosis.

**Why the Correct Answer is Right:**
The correct answer, D. Lung fibrosis, is not a part of the Garland sign in sarcoidosis because lung fibrosis is a late complication of the disease, often seen several years after the initial diagnosis and treatment. In contrast, the Garland sign primarily represents early findings related to the inflammatory process.

**Why Each Wrong Option is Incorrect:**
A. Centrilobular nodules (Option A) are a common finding in sarcoidosis and represent the presence of granulomas in the pulmonary parenchyma.
B. Interlobular septal thickening (Option B) indicates the presence of granulomas, which are the primary component of the Garland sign.
C. Pleural effusion (Option C) is a less common feature in the early stages of sarcoidosis and is usually seen in more advanced cases.

**Clinical Pearl:**
In clinical practice, the Garland sign serves as a valuable tool for diagnosing sarcoidosis, particularly when combined with other radiological findings. Recognizing these early radiological features can lead to timely diagnosis and initiation of appropriate treatment, which is crucial as early intervention can prevent or manage complications related to the disease progression.