Firstly, these are two completely different diseases. Thromboangiitis obliterans is an inflammatory vascular disease involving the medium and small veins and arteries, causing migratory superficial phlebitis and leading to the obstruction of the veins, as well as some obstructions in the lower limb arteries. Thus, thromboangiitis obliterans includes some obliterative diseases of both arteries and veins, the cause of which is an autoimmune inflammation.

Varicose veins are one of the most common vascular surgical diseases. They primarily manifest as tortuous, clustered, and dilated superficial veins of the lower limbs. This condition does not involve arterial changes, but varicose veins can progressively worsen and may lead to pigmentation and ulceration, which at that time necessitates differentiation from arterial ulcers. Generally, the ulceration in varicose veins is located in the "gaiter area," which is the area covered by a boot when wearing one, including the lower one-half to one-third of the lower leg. Most of the ulcers from varicose veins primarily appear above the inner ankle.

The ischemia caused by thromboangiitis obliterans leads to a dry-type ischemia, where the limbs can gradually become dry, shriveled, atrophied, and blackened, with ulcers typically beginning from the extremities.