Does Monosodium Urate Crystal Vascular Deposition Exist? Review of the Evidence

Abstract

Cardiovascular disease in gout is a central issue, but the underlying mechanisms linking the two are unclear. The existence of monosodium (MSU) crystal deposition directly inflaming vessel walls has been recurrently suggested and challenged since the 1950s and is again a matter of active debate since recent studies using dual-energy computed tomography (DECT) suggested a higher prevalence of plaques considered to be containing MSU crystals in patients with gout. The objective of this review is to critically cover the evidence gathered on MSU crystal deposition in the cardiovascular system. In patients affected with gout, histological evidence of MSU crystals in arteries lacks a biochemical characterization supporting the observation in polarized light microscopy, while current knowledge on vascular lesions identified in DECT as containing MSU crystals suggests that they may be only artifacts, including in cadaveric and phantom studies. In individuals without gout, MSU crystal deposition in vessel walls have not been demonstrated, despite higher urate local plaque concentrations and increased xanthine oxidase activity. Gout is associated with increased arterial calcification and atherosclerosis, both being potential confounders of suspected MSU crystal deposition for the analysis of DECT scans and histopathology, respectively. In summary, the reality of the presence of MSU crystals in vascular plaques has not been demonstrated so far, and needs further investigation as it represents a potential outcome for cardiovascular complications of gout.