Multifocal Fibromuscular Dysplasia in a Horseshoe Kidney: Coincidence or Consequence?

Spontaneous coronary artery dissection (SCAD) is increasingly identified as a significant cause of acute coronary syndrome and is often associated with fibromuscular dysplasia (FMD), a non-atherosclerotic, non-inflammatory vascular disease affecting medium-sized arteries. SCAD and FMD frequently co-occur, warranting extracoronary vascular imaging. Horseshoe kidney, a rare congenital anomaly, has been linked to various genitourinary and vascular abnormalities but has not previously been associated with FMD. A man in his early 50s presented with acute chest pain and was diagnosed with SCAD of the obtuse marginal artery. Due to the known association between SCAD and FMD, CT angiography was performed, revealing a horseshoe kidney and a classic string-of-beads appearance in both renal arteries, consistent with multifocal FMD. No abnormalities were found in other vascular beds, and there was no clinical evidence of connective tissue disorders. Renal function was normal, and hypertension was well controlled with antihypertensive medication. The patient was managed conservatively and remains under outpatient follow-up. This is the first reported case of coexisting renal artery multifocal FMD and a horseshoe kidney. While the co-occurrence may initially appear coincidental, the rarity of both conditions suggests a potential, previously unrecognized congenital or biomechanical association. One could hypothesize that the abnormal positioning and limited mobility of the fused kidneys in a horseshoe kidney might contribute to chronic vascular wall stress and arterial remodeling. Further research is warranted to assess the prevalence of FMD in patients with horseshoe kidneys and to explore possible shared developmental or mechanical mechanisms.