Fibromuscular Dysplasia: State of the Science and Critical Unanswered Questions

Abstract

Fibromuscular dysplasia (FMD) is nonatherosclerotic, noninflammatory vascular disease that may result in arterial stenosis, occlusion, aneurysm, or dissection.1–3 The cause of FMD and its prevalence in the general population are not known.4 FMD has been reported in virtually every arterial bed but most commonly affects the renal and extracranial carotid and vertebral arteries (in ≈65% of cases).5 The clinical manifestations of FMD are determined primarily by the vessels that are involved. When the renal artery is involved, the most frequent finding is hypertension, whereas carotid or vertebral artery FMD may lead to dizziness, pulsatile tinnitus, transient ischemic attack (TIA), or stroke. There is an average delay from the time of the first symptom or sign to diagnosis of FMD of 4 to 9 years.5,6 This is likely because of a multitude of factors: the perception that this is a rare disease and thus FMD is not considered in the differential diagnosis, the reality that FMD is poorly understood by many healthcare providers, and the fact that many of the signs and symptoms of FMD are nonspecific, thus leading the clinician down the wrong diagnostic pathway. A delay in diagnosis can lead to impaired quality of life and poor outcomes such as poorly controlled hypertension and its sequelae, TIA, stroke, dissection, or aneurysm rupture. It should also be noted that FMD may be discovered incidentally while imaging is performed for other reasons or when a bruit is heard in the neck or abdomen in an asymptomatic patient without the classic risk factors for atherosclerosis. The first description of FMD is attributed to Leadbetter and Burkland7 in a 5½-year-old boy with severe hypertension and a renal artery partially occluded by an intra-arterial mass of smooth muscle. He underwent a unilateral nephrectomy of an …