## **Core Concept**
Takayasu's arteritis is a large vessel vasculitis that primarily affects the aorta and its major branches. The disease is characterized by inflammation of the arterial walls, leading to stenosis, occlusion, or dilation of the affected vessels. Aortography is a diagnostic tool used to visualize the aorta and its branches.

## **Why the Correct Answer is Right**
The most commonly affected arteries in Takayasu's arteritis, as seen by aortography, include the **subclavian arteries**, followed by the **common carotid arteries**, and the **aorta** itself. The subclavian arteries are frequently involved, leading to symptoms such as arm claudication, decreased blood pressure, and diminished pulses in the affected limb. The involvement of these arteries is a hallmark of the disease and is critical for diagnosis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While the **renal arteries** can be involved in Takayasu's arteritis, leading to renovascular hypertension, they are not the most commonly affected arteries seen by aortography.
- **Option B:** The **iliac arteries** can also be involved, but they are less frequently affected compared to the subclavian and carotid arteries.
- **Option D:** The **vertebral arteries** may be involved, but similar to the renal and iliac arteries, they are not the most commonly affected.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl in Takayasu's arteritis is the "reverse coarctation" phenomenon, where there is stenosis or occlusion of the **subclavian arteries** and/or **aorta**, leading to high blood pressure in the legs but low blood pressure in the arms. This presentation can be a critical clue to the diagnosis.

## **Correct Answer:** .