**Question:** Most common organs involved in Wegener's granulomatosis are:

A. Lungs
B. Kidneys
C. Brain
D. Heart

**Core Concept:** Wegener's granulomatosis is a rare autoimmune disorder characterized by inflammation and granuloma formation in various organs, particularly affecting the kidneys, lungs, and upper respiratory tract. It is associated with the autoimmune response against the neutrophil granulocytes.

**Why the Correct Answer is Right:** Wegener's granulomatosis primarily targets the kidneys (glomerulonephritis), leading to proteinuria, hematuria, and hypertension. The disease also affects the lungs, causing diffuse alveolar hemorrhage and bronchiectasis. Since the disease involves the upper respiratory tract, the lungs and kidneys are the most commonly involved organs.

**Why Each Wrong Option is Incorrect:**

A. Lungs: Although lungs are affected in Wegener's granulomatosis, the correct answer should specify the involvement of both alveoli and bronchi.
B. Kidneys: While the disease primarily targets the kidneys, the correct answer should emphasize the presence of c-ANCA (anti-neutrophil cytoplasmic antibodies) and necrotizing glomerulonephritis.
C. Brain: Wegener's granulomatosis predominantly affects the lungs, kidneys, and upper respiratory tract, making the brain involvement less common.
D. Heart: Wegener's granulomatosis primarily affects the lungs and kidneys, making heart involvement less common in this disease.

**Clinical Pearl:** Wegener's granulomatosis is considered a vasculitis, as it involves inflammation and damage to blood vessels. Detection of c-ANCA (anti-neutrophil cytoplasmic antibodies) in the blood is a diagnostic clue for Wegener's granulomatosis and helps differentiate it from other vasculitides.

**Correct Answer:** B. Kidneys (glomerulonephritis)

**Why the Correct Answer is Right:** Wegener's granulomatosis is characterized by granuloma formation in the affected organs, which leads to inflammation and damage of blood vessels. In the case of the kidneys, Wegener's granulomatosis presents as necrotizing glomerulonephritis, leading to proteinuria, hematuria, and hypertension. The presence of c-ANCA (anti-neutrophil cytoplasmic antibodies) is a crucial diagnostic clue for Wegener's granulomatosis.

**Why Each Wrong Option is Incorrect:**

A. Lungs: While lungs are indeed affected, the correct answer should focus on the necrotizing alveolitis and bronchiectasis as well as the presence of c-ANCA.
C. Brain: The disease primarily affects the lungs, kidneys, and upper respiratory tract, making brain involvement less common.
D. Heart: Wegener's granulomatosis primarily affects the lungs, kidneys, and upper respiratory tract, making heart involvement less common.