**Question:** Most common site in respiratory tract for amyloidosis is:

A. Trachea
B. Bronchi
C. Alveoli
D. Lungs

**Core Concept:** Amyloidosis is a group of diseases characterized by the extracellular deposition of amyloid fibrils, which are insoluble protein aggregates, leading to organ dysfunction.

**Why the Correct Answer is Right:**
Amyloidosis primarily affects the respiratory system when it occurs in the respiratory tract. In this case, amyloid deposits are found in the submucosa of bronchi, which are large airways within the lungs. The correct answer, **Bronchi**, is chosen because the submucosal glands and smooth muscles of the bronchi are affected in this situation.

**Why Each Wrong Option is Incorrect:**
A. **Trachea (Option A)**: Amyloidosis in the trachea is rare, and the disease primarily affects bronchi and lungs.

C. **Alveoli (Option C)**: Amyloidosis primarily affects the submucosa of bronchi and lungs, not the alveoli, which are tiny air sacs in the lungs responsible for gas exchange.

D. **Lungs (Option D)**: Although lungs can be affected in systemic amyloidosis, the correct answer is bronchi because the amyloid deposits are found in the submucosal glands and smooth muscles of the bronchi in primary pulmonary amyloidosis.

**Clinical Pearl / High-Yield Fact:**
Primary pulmonary amyloidosis is a rare form of amyloidosis that primarily affects the lungs and respiratory tract. In this situation, amyloid deposits are found in the submucosal glands and smooth muscles of the bronchi and other respiratory structures. Understanding this distinction helps differentiate between primary pulmonary amyloidosis and other respiratory diseases and guides treatment options.

**Correct Answer:** Bronchi (Option B)