Fibromuscular dysplasia (FMD) is defined as a nonatherosclerotic, noninflammatory lesion of the arterial wall characterized by disrupted architecture and abnormal mesenchymal cellular proliferation [1]. The etiology remains poorly understood and explained, likely related to various genetic and environmental factors [2,3]. The majority of patients (up to 90 %) with FMD are women, and the most commonly affected anatomic locations include the renal, extracranial carotid, and vertebral arteries. Men can also develop FMD and appear to have more aggressive clinical behavior, with a higher frequency of aneurysms and dissections as complications [4,5].

The classical histological classification recognizes a few histological patterns that affect the intima, media, or adventitia. Intimal lesions, known as intimal fibroplasia, resemble atherosclerosis but do not contain lipids and inflammatory cells. The most common medial alterations include medial fibroplasia, perimedial fibroplasia, and medial hyperplasia, which are characterized by abnormally oriented smooth muscle cells with fibrosis, fibrous bands in the outer media, and hyperplasia of smooth muscle cells, respectively. Circumferential adventitial fibrosis with unaffected media and intima is termed periarterial (adventitial) fibroplasia [6].

However, the current clinical classification of FMD does not rely on histopathology but on angiographic findings. The consensus document from 2019 divides FMD into two groups: focal (occurring in any part of the artery) and multifocal (with alternating areas of stenosis and dilations, the so-called string of beads). Although FMD is primarily considered a stenotic lesion, manifestations such as aneurysm, dissection, and arterial tortuosity are recognized. Depending on the clinicopathological scenario, treatment includes endovascular angioplasty or surgical resection of the affected artery [1].

Herein, we present a case of FMD affecting a subclavian artery as an uncommon site and review similar cases in the discussion.