Overview

Discover the latest insights into the epidemiology and risk factors for Fibromuscular Dysplasia (FMD). Learn about the hormonal, genetic, and lifestyle influences on this rare vascular condition. ​​Fibromuscular Dysplasia (FMD) is a complex and rarely occurring vascular disorder that can significantly impact one's health, especially women.¹ Understanding the epidemiology and risk factors associated with FMD is crucial for early diagnosis and effective management. This article will provide you with a clear explanation of FMD's epidemiology and risk factors, ensuring you have the information you need to navigate this condition confidently.

Epidemiology and risk factors for Fibromuscular Dysplasia

Fibromuscular Dysplasia (FMD) affects the arterial walls, causing them to narrow, enlarge, or develop abnormal cell growth.¹ This non-inflammatory condition replaces strong cells in the arteries with weaker, fibrous cells, increasing their susceptibility to damage due to changes in artery composition.² The condition is often underdiagnosed due to its nonspecific symptoms, which can range from high blood pressure to headaches and dizziness. Understanding these risk factors can aid in early detection and better management of FMD. 

Understanding Fibromuscular Dysplasia (FMD)

The word ‘dysplasia’ stems from the Greek word ‘dys’, defining bad and the term ‘plasia’ meaning to change or conform.³ Fibromuscular Dysplasia (FMD) is a rare, non-inflammatory, nonatherosclerotic vascular condition that influences medium-sized arteries.^1,4 It involves abnormal cellular growth within the arterial walls, leading to the development of arterial stenosis, aneurysms, occlusions, or dissections.⁴ An artery allows healthy contractions and expansions for blood to rhythmically flow through the body; however, FMD-affected arteries may be overly stiff or not stiff enough.² 

Whilst FMD commonly occurs in renal and cervical arteries, it can affect any vascular bed, making the extent of this disorder varied and consisting of a wide range of symptoms.^3,5 Renal artery-induced FMD is the most common, accounting for 58% of all cases¹. The associated organs can assist in the determination of symptoms, such as renal artery stenosis inducing hypertension symptoms and carotid stenosis influencing paralysis and headaches.^3,6 Furthermore, patients experiencing numerous vascular beds indicate that FMD may not be a localised disorder.³ From an angiographic aspect, two subtypes have been derived, known as multifocal and focal FMD.⁷

Studying FMD meticulously is vital, as even children, young women, and anyone can be at risk.² A prominent understanding of this disorder can help detect early signs for prompt treatment. 

What is Fibromuscular Dysplasia?

FMD is characterised by a range of complications, some common symptoms being hypertension, headaches, and dizziness.^1,2 Potential complications can include renal artery stenosis, stroke, and aneurysms.² While FMD commonly presents itself as renovascular hypertension, it can also lead to strokes in young women and adults.¹ 

The main locations of Fibromuscular Dysplasia include the renal arteries associated with the kidneys, and vertebral and carotid arteries linked to the brain.² However, FMD can affect any arterial bed in the body, with the potential to be present in multiple areas simultaneously.^1,2 Around 75% of FMD cases involve the carotid artery.⁸

A common subtype of fibromuscular dysplasia is multisite, depicted by a ‘string of beads, ’ which can affect multiple vascular beds.^3,5 This phenotypic detection on angiography helps in diagnosis.¹ The artery consists of three main layers that coexist from a histological context: intimal, medial and perimedial.^2,7 The tunica media, also referred to as the middle layer, is the most common form of FMD. Its thickness and high elastin content make it prone to the loss of the elastic membrane alongside variations in ridges of collagen.^1,2 Appearances of medial FMD include the ‘string of beads’, detected through methods like Computed tomography angiography (CTA).¹ 

Epidemiology of Fibromuscular Dysplasia

Prevalence and incidence

Fibromuscular Dysplasia is a rare vascular disease, but its exact prevalence and incidence rates are challenging to determine. Studies suggest that renal FMD influences approximately 0.4% of the overall population.¹ The prevalence of FMD varies globally; however, as it is a rare disease, more data is collected from the United States and Europe.⁹ 

 Demographic Patterns

Whilst FMD can affect any age, there are still uncertainties on the age distribution of this disorder.^3,4 FMD predominantly affects middle-aged women, where most cases are present in women under the age of 50 years, with the median age being 48 years.¹ Women are three times more likely to develop FMD than men.¹ Specifically, the subtype multifocal FMD, which constitutes around 80% of cases, is more common in women.⁷ Focal FMD is scarce and exhibits a more equal gender ratio.⁷ While there are not many racial disparities in FMD, it appears to be more common in Caucasians compared to Black individuals.^1,7 However, further comprehensive data is required on this.

Challenges in understanding epidemiology

Despite advances in research, the causes and epidemiology of FMD remain difficult. Several studies have used data on renal transplant donation, cerebral angiography, and autopsy studies to evaluate FMD patients, making research have numerous limitations for the collective population.¹⁰ 

Risk factors for Fibromuscular Dysplasia

Genetic factors

Whilst the aetiology is still a mystery, genetics and hormonal influence do contribute to FMD development.³ Environmental and genetic risk factors have been associated with FMD, where a percentage of FMD cases do seem to have genetic involvement.^1,2 It has been stated that fibromuscular dysplasia is inherited as a dominant trait, with increased penetrance in females than males.³ A study from Perdu and colleagues (2007) indicated that 52% of relatives from parents’ history of FMD exhibited similar phenotypical abnormalities within arteries.³ High chances of familial relations of FMD can lead to aortopathy from gene variants.^3,11

Hormonal influences

As the disorder has a female predominance, it has been investigated whether FMD is related to hormonal influences such as oestrogen and other hormonal contributors.^2,5 The role of these hormones in FMD development and their correlation with the female gender and reproductive age have been significant areas of study, as there is no firm evidence on pregnancy or contraception increasing FMD development.¹²

Environmental and lifestyle factors

Tobacco smoking is another huge risk factor for the manifestation of fibromuscular dysplasia.³ Smoking is a major risk for heart disease, and those who smoke with FMD have increased chances of facing sufferable arterial symptoms.¹²

Diagnostic challenges and methods

FMD has the potential to exist without evident symptoms, hence, diagnosis remains challenging until evident symptoms appear, such as dissection or aneurysm.² A doctor can confirm diagnosis through various methods, although the most frequent method of FMD diagnosis is vascular imaging.^1,2 A few more to mention include:

• Duplex ultrasonography/ultrasound: A first-line method for FMD testing¹
• Magnetic resonance angiography (MRA)
• Digital subtraction angiography: The most standard imaging approach for FMD⁶ 
• Arteriography: Employ a pressure gradient to detect FMD¹
• Computed tomography angiography (CTA): A great tool for diagnosis of FMD, helpful in detecting appearances of medial FMD¹

Management and treatment of FMD

Specialised physicians are essential in treating FMD, offering personalised plans to monitor your own response to treatments.² Aspirin may be provided to prevent blood clotting alongside other potential medication combinations.^1,2 Frequent scans will be taken to ensure treatment effects are sustained.² Symptoms can vary in each individual based on the type of FMD.² Renal FMD may be treated with an Angiotensin-converting enzyme inhibitor (ACE-1) alongside other antihypertensives to monitor hypertension.¹ Angioplasty may also be recommended.¹ Whilst confirmations through biopsies are rare, initial radiological and clinical data are derived from the patient for diagnosis.³ 

Whilst there are medications to help treat FMD, controlling the risk factors associated with FMD is also vital.¹ Implementing dietary and lifestyle changes are recommended, including quitting smoking and reducing excess salt intake to prevent blood pressure spikes.^2,13 Incorporating daily exercise is excellent for maintaining great arterial health, reducing blood pressure, and allowing arteries to stay wide and be more flexible.¹⁴ While aerobic exercise like cardio is good, pairing it with resistance training is also a great option.^2,14 Increasing muscle mass allows the cardiovascular system to have locations of blood to be pumped to, subsequently reducing pressure on the arteries.¹⁴ However, it is important to consult a doctor before starting any new exercise regimen, especially those with a history of dissection or aneurysm.¹² 

Here are some key recommendations:

• Quit Smoking: Significantly reduces risks of arterial damage and complications ²
• Reduce Salt Intake: Prevent blood pressure spikes that could impact your arteries
• Daily Exercise: Aerobic activities like cardio and resistance training

FAQ’s

What are the first signs of Fibromuscular Dysplasia (FMD)?

Recurrent initial symptoms of FMD consist of increased blood pressure, headaches, and dizziness. If you experience these symptoms, it is important to seek medical advice for proper evaluation and diagnosis.

How is FMD different from other vascular diseases?

There are various diseases present within the FMD spectrum, hence, biopsies and other examinations can help differentiate and confirm the disease.³ It can be differentiated from similar disorders, including Marfan syndrome, Alport syndrome, Ehlers-Danlos syndrome and alpha-1 antitrypsin deficiency.¹ This can be differentiated by specialists through phenotypic and genetic analyses.¹ Unlike vasculitis, FMD does not involve visible inflammation.¹ 

Can FMD increase the risks towards pregnancy complications?

There is no sufficient evidence to prove that pregnancy heightens the development of FMD ¹². Patients with FMD have had pregnancies and safe deliveries without complications. However, hypertension may increase during pregnancy, so it is crucial to consult your doctor and have your blood pressure regularly checked.¹²

Summary

Fibromuscular Dysplasia (FMD) is a non-atherosclerotic, non-inflammatory arterial disease that primarily affects women and can lead to serious complications such as aneurysms, hypertension, and strokes. FMD is more commonly found in middle-aged women, with potential risk factors such as genetic predispositions, hormones, and environmental contributors.^1,4

Early detection and personalised treatments are crucial in effectively managing FMD. Increased awareness among the public, along with dedicated research funding, are essential to improve diagnosis rates, treatment options, and thus patient outcomes.