**Question:** On chest radiology, "egg-shell calcification" is seen in:

A. Aneurysm
B. Pulmonary tuberculosis
C. Congenital heart diseases
D. Chronic calcified infective endocarditis

**Core Concept:** Egg-shell calcification refers to a characteristic radiological finding seen in certain pathologies involving calcification. It represents a thin, irregular, and faintly radio-opaque layer surrounding a more dense central area.

**Why the Correct Answer is Right:**

In this case, egg-shell calcification is typically observed in D. Chronic calcified infective endocarditis. In this condition, bacteria (usually Staphylococcus aureus or Streptococcus spp.) infect the heart valves, leading to inflammation, fibrosis, and calcification. The egg-shell appearance results from the initial, thin, and irregular calcification surrounding a central area of dense calcification due to the calcified bacterial endocardium.

**Why Each Wrong Option is Incorrect:**

A. Aneurysm: Egg-shell calcification is not a characteristic feature of aneurysms, which are localized dilations or bulging of blood vessels due to weakness in the vessel wall.

B. Pulmonary tuberculosis: Egg-shell calcification is not a common finding in pulmonary tuberculosis, although calcification may occur in some cases. The characteristic findings in pulmonary tuberculosis are more likely to involve tree-in-bud pattern and caseating nodules.

C. Congenital heart diseases: Egg-shell calcification is not a specific feature for congenital heart diseases. The radiological findings depend on the specific congenital heart defect and may vary.

**Clinical Pearl:** Understanding egg-shell calcification helps in differentiating between various conditions involving calcification, such as infective endocarditis versus aneurysms or congenital heart diseases, which have distinct imaging features. This can aid in making an accurate diagnosis, guiding further management and treatment decisions.