What is the underlying pathophysiology of fibromuscular dysplasia?

Fibromuscular dysplasia (FMD) is characterized by abnormal growth patterns in the vascular walls that primarily affect medium-sized arteries. The underlying pathophysiology involves medial hyperplasia, which is the proliferation of smooth muscle cells in the tunica media layer of the arterial wall. This leads to a distinctive "string of beads" appearance on imaging, as alternating areas of stenosis (narrowing) and aneurysm formation can occur due to this hyperplasia.

In particular, the medial hyperplasia causes arterial stenosis by thickening the arterial wall and reducing the lumen's diameter, which can compromise blood flow and result in various clinical manifestations, such as hypertension or ischemia in the areas supplied by the affected vessels. Understanding this mechanism is crucial for diagnosing and managing patients with fibromuscular dysplasia effectively.