What Is Fibromuscular Dysplasia?

Fibromuscular dysplasia, or FMD, is a rare medical condition where there's abnormal growth within the walls of the arteries. This can lead to the arteries narrowing or bulging, affecting blood flow. It's not caused by the usual suspects like cholesterol buildup, so it is a unique issue primarily affecting the muscular arteries in our body.

This article will dive deeper into the causes, symptoms, and management strategies for FMD. 

Key information

• Fibromuscular dysplasia (FMD) has a significant impact on the walls of the arteries, causing them to become either overly fragile or excessively rigid. 
• These changes can result in grave issues, such as the arteries narrowing (stenosis), bulging or weakening (aneurysm), or even tearing (dissection) 
• A striking majority of adults diagnosed with FMD are people assigned female at birth (AFAB). FMD is more than four times as frequent in AFAB people compared to those assigned male at birth (AMAB)¹
• Those with FMD must be vigilant for severe symptoms, adhere to regular medical examinations, and avoid smoking.

Introduction

Fibromuscular dysplasia (FMD) is a collection of arterial diseases that aren't caused by inflammation or atherosclerosis (narrowed blood vessels due to fatty substance buildup). These diseases mainly target the renal arteries and carotid arteries.¹ In simple terms, FMD is a rare condition where there's unusual growth within the walls of our arteries, causing them to either narrow or bulge, which can interfere with our blood flow.2 This isn't due to the common culprits like cholesterol buildup; it's a unique issue affecting the muscular arteries in our body.³ Knowing about FMD is essential because it can lead to serious health problems like high blood pressure, artery damage, and even stroke.²

Understanding the basics

Fibromuscular dysplasia (FMD) is a disease that affects multiple arteries in the body. Even if the disease is only evident in one artery, there might be hidden lesions in other arteries. Interestingly, there seems to be a family connection in about 10% of FMD cases.¹ 

FMD is linked to abnormal cell growth in the walls of our larger arteries. This can cause these arteries to narrow, balloon out, or even tear.² While FMD can occur in any artery, it's most likely to affect the renal (kidney) arteries and carotid (neck) arteries.² In fact, it's been reported to show up in most arteries throughout the body at one time or another.³

Causes and risk factors

The root cause of fibromuscular dysplasia (FMD) remains a mystery. Some scientists think it might be a mix of our genes, hormone levels, smoking and even physical forces in the body.^3,4 While some theories suggest hormonal and mechanical factors might play a role, the familial occurrence in some instances hints at a genetic link.¹ However, we do know that FMD is more common in those AFAB and is usually diagnosed in people 50 and younger.²

Symptoms and presentation

Just because someone has fibromuscular dysplasia (FMD) doesn't mean they'll notice any symptoms. Many people with FMD feel just fine. But when symptoms do show up, they depend on which artery is affected. For example, if the carotid arteries in the neck are affected, someone might get headaches or pulsatile tinnitus, resulting in a swooshing sound in their ears.² Moreover, when FMD affects the cervicobrachial region, where the cervical spine (neck) meets the skull, complications can arise, such as artery tearing, leading to symptoms like:¹

• Severe headaches 
• Horner's syndrome
• Stroke

There's also a risk of brain aneurysms, which can result in bleeding within the brain.¹ 

But, if the renal arteries near the kidneys are the culprits, it could lead to high blood pressure (renal hypertension) or even kidney problems.²

When FDM affects the blood vessels that go to your intestines, it can cause:³

• Unspecific abdominal pain
• Diarrhoea
• Nausea
• Vomiting

Diagnostic approaches

Sometimes, during a physical check-up, a doctor might hear an unusual sound (called a bruit) over an affected artery.² If a doctor suspects fibromuscular dysplasia (FMD), they might use non-invasive imaging tests such as duplex ultrasound, MRI angiography, and CT angiography to get a closer look at the artery.^1,2

While catheter angiography is the gold standard for diagnosing FMD, it's an invasive method. In this procedure, a catheter (a thin, flexible tube) is inserted into a large blood vessel, usually in the groin or arm, and guided to the area of interest. A contrast dye is then injected through the catheter, and X-ray images are taken to visualise the blood vessels. This is usually reserved for cases where immediate treatment during the procedure might be necessary. 

And while there's no specific blood test for FMD, doctors might run some tests to rule out other conditions.² 

Treatment and management

For those with high blood pressure due to fibromuscular dysplasia (FMD), treatments range from blood pressure medications to angioplasty (surgery to widen the artery) for severe cases. In more intricate situations, reconstructive surgery might be needed.¹ If a brain aneurysm bursts, treatments could involve neurosurgical clipping or endovascular coiling.¹ Generally, the progression of FMD in the renal artery is slow and rarely leads to kidney failure due to a lack of blood supply.¹

Managing FMD is all about the location and severity of the disease. Some patients might just need medications, like those for blood pressure. Other therapeutic options for FMD may include antiplatelet and antithrombotic therapy to prevent blood clotting.³ And for everyone with FMD, regular check-ups and steering clear of tobacco is good practice.²

Prevention and early detection

While we can't exactly prevent fibromuscular dysplasia, being aware of its symptoms can help with early detection.² Given the suspicion that FMD might have genetic components and can run in families, it's crucial to be aware of your family's health history and share this information with your healthcare provider.^2,4 Regular check-ups are the keys to early detection and effective management of this condition.²

Summary

Fibromuscular dysplasia (FMD) is a unique arterial disease that doesn't stem from inflammation or atherosclerosis. It primarily targets the renal (kidney) arteries and carotid (neck) arteries. While its exact origins are still under investigation, there's evidence suggesting it might run in families. Diagnosis is mainly through imaging tests and angiography, and treatments are tailored based on the disease's severity and location.¹ In a nutshell, understanding FMD is the first step to early diagnosis and effective management. If you or someone you know is showing symptoms or thinks they might be at risk, don't hesitate to reach out to a healthcare professional for a proper check-up.²