Cholesterol Crystal Embolization Exacerbates Critical Limb Ischemia

Chronic life-threatening ischemia (CLTI), characterized by chronic severe ischemic ulcers or gangrene in the legs with arterial occlusive disease, has a high rate of amputation and mortality. However, how lower extremity artery disease (LEAD) leads to CLTI is not fully understood yet. Here, we report a 79-year-old man with resting pain and gangrene in the left first and fifth toes for a year who had undergone repetitive endovascular treatment (EVT) that temporarily improved the ischemia. Non-obstructive general angioscopy (NOGA) revealed yellow and red floating emboli at the occluded left superficial femoral artery (SFA). Although a second EVT for the reoccluded SFA was successful, amputation of the left lower knee remained necessary because of osteomyelitis of the left heel. Cholesterol crystals (CCs) associated with innate inflammation were detected in spontaneously ruptured aortic plaques (SRAPs) via aortic screening using the NOGA, in occluded SFAs, and on the surface of the muscle cross-section of the amputated legs via a polarizing microscope. Histopathological analysis demonstrated CCs in small vessels in various stages of patchy necrosis and muscle regeneration. In this case, the process of CC embolization, such as the embolic source of CCs, occlusion in arteries, small arteries, and deposition in muscles, was confirmed in CLTI. CCs are the principal trigger of IL-6 production through the innate inflammatory response in spontaneously ruptured aortic plaques. Mechanical ischemia and chronic inflammation due to embolized CCs may cause chronic limb damage. In this case, the CC embolization might exacerbate CLTI.