Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Inhibitors: A Novel Therapy in the Treatment of Cholesterol Crystal Embolism-Induced Kidney Injury.

Cholesterol crystal embolism (CCE) is a challenging and often underrecognized cause of kidney impairment, especially in elderly patients with significant atherosclerotic disease. CCE typically arises from dislodged cholesterol crystals that migrate from atherosclerotic plaques to occlude small renal and systemic arteries. Here, we report a case of a 72-year-old man who presented with acute kidney injury following coronary artery bypass graft surgery. Five weeks postsurgery the patient experienced a rapid decline in kidney function. Kidney biopsy confirmed the diagnosis of CCE, showing cholesterol clefts and associated inflammation within renal arteries. Although the patient initially responded to high-dose corticosteroid therapy kidney function declined during steroid tapering. A proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor, evolocumab, was introduced as an adjunct treatment, targeting lipid reduction and plaque stabilization. Following initiation of evolocumab, kidney function stabilized and gradually improved, with concurrent reductions in eosinophilia, suggesting a decrease in ongoing embolic phenomena. This case illustrates the potential role of PCSK9 inhibitors as an adjunctive therapy for CCE-associated kidney injury, particularly when conventional management may be insufficient. PCSK9 inhibitors warrant further investigation in CCE cases with kidney involvement, as they may offer additional benefits beyond lipid lowering by reducing plaque instability and associated microinflammation.