## **Core Concept**
The "string of beads" sign is a radiological finding typically associated with a specific vascular condition. It refers to the appearance of a series of narrowed and dilated segments in an artery, resembling a string of beads. This sign is most commonly seen in conditions that affect the arterial walls.

## **Why the Correct Answer is Right**
The correct answer, **C. Fibromuscular dysplasia**, is right because fibromuscular dysplasia (FMD) is a vascular disease characterized by the presence of non-atherosclerotic, non-inflammatory lesions in medium and large arteries, most commonly the renal and internal carotid arteries. The "string of beads" appearance on angiography is pathognomonic for FMD due to the alternating areas of stenosis and dilatation.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Atherosclerosis typically presents with diffuse or focal narrowing of arteries due to plaque buildup and does not characteristically produce a "string of beads" appearance.
- **Option B:** Vasculitis involves inflammation of the blood vessels and can cause a variety of angiographic findings, including stenosis and aneurysms, but it is not classically associated with the "string of beads" sign.
- **Option D:** Artherosclerotic aneurysm would more likely show as a localized dilatation rather than the characteristic pattern of alternating stenosis and dilatation.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the "string of beads" sign is highly suggestive of fibromuscular dysplasia, particularly in young women presenting with renovascular hypertension. Early recognition of this condition is crucial for appropriate management, which may include angioplasty.

## **Correct Answer:** C. Fibromuscular dysplasia.