What are the key clinical features that suggest a diagnosis of Fibromuscular Dysplasia (FMD) in a patient presenting with unexplained hypertension?

Key clinical features suggesting fibromuscular dysplasia (FMD) in a patient with unexplained hypertension include:

• Onset of hypertension at a young age, especially in women under 50 years old, as FMD predominantly affects younger females.
• Resistant or difficult-to-control hypertension despite standard treatment, raising suspicion for secondary causes such as renal artery involvement by FMD.
• Absence of typical atherosclerotic risk factors, which helps differentiate FMD from atherosclerotic renal artery stenosis.
• Presence of characteristic vascular abnormalities on imaging, such as the classic 'string of beads' appearance in the renal arteries, although this is a diagnostic feature rather than a clinical symptom.
• Associated symptoms or signs of arterial involvement beyond the renal arteries, including headaches or pulsatile tinnitus if carotid or vertebral arteries are affected, which may accompany hypertension.

These features align with NICE guidance on investigating secondary hypertension, which highlights the importance of considering FMD in younger patients with unexplained or resistant hypertension NICE NG136. Recent genetic and clinical studies Warchol-Celinska et al. 2020 further support that FMD often presents with these clinical patterns and may have a genetic predisposition influencing its vascular manifestations, reinforcing the need for targeted vascular imaging in suspected cases Kirton et al. 2013Warchol-Celinska et al. 2020.