Limb ulcers are an important complication of systemic scleroderma, and persistent and recurrent ulcers can cause severe pain, infection, gangrene, functional impairment, and decreased quality of life, causing great suffering to patients. Because of this, the study of scleroderma limb ulcers has become a hot research issue in recent years. The following diseases may also cause limb ulcers: 1, popliteal aneurysm Popliteal aneurysm is one of the more common aneurysms in peripheral vascular aneurysms, mostly atherosclerotic aneurysms, followed by injury aneurysms. The management of popliteal aneurysms occupies a special place in the history of vascular surgery. As early as the 4th century, Antyllus performed the first popliteal aneurysm surgery. For several years, the procedure was limited to arterial ligation. In 1916, Berheim reported the use of a saphenous vein interposition graft to reconstruct popliteal aneurysm resection, and in 1958, Crawford published the results of popliteal aneurysm surgery with an artificial vessel. The surgical approach is becoming more reasonable and effective. 2, lower extremity atherosclerosis occlusive disease Atherosclerosis occlusive disease is a degenerative disease, is the basic pathological process of large and medium arteries, mainly abnormal deposition of cells, fibrous matrix, lipids and tissue debris, in the arterial intima or middle layer of the complex pathological changes in the process of proliferation. Among peripheral vascular disorders, almost most of the narrowing, occlusive or aneurysmal lesions of arteries are caused by atherosclerosis. Atherosclerotic lesions are generally systemic disorders that occur in certain large and medium-sized arteries, such as the lower abdominal aorta, iliac artery, femoral artery, and popliteal artery, but rarely in the upper limb arteries. The arteries are thickened, stiffened, with atheromatous plaque and calcification, and may be followed by thrombosis, resulting in narrowing or occlusion of the arterial lumen and ischemic symptoms in the limbs. The affected limb has clinical manifestations such as coldness, numbness, pain, intermittent claudication, and ulceration or necrosis of the toe or foot. Sometimes the stenosis or occlusive lesion is segmental and multiplanar, and it usually occurs at the beginning of the bifurcation of the artery and the posterior wall of the lumen, and the bending part of the arterial trunk is also more often involved. 3, overlap syndrome Overlap syndrome refers to the overlap between two or more connective tissue diseases, also known as overlapping connective tissue disease. OS usually occurs in six diffuse CTDs, namely SLE, RA, DM/PM, PSS, nodular CTD, and PM. PM, PSS, polyarteritis nodosa (PN) and rheumatic fever (RF) overlap, and also from 6 CTDs with proximal diseases such as leukoaraiosis, dry syndrome, lipofuscinosis, in addition to other autoimmune diseases such as chronic thyroid cholangitis, autoimmune hemolytic anemia, etc. Erythromelalgia is a peripheral vasodilatory disease of unknown origin, characterized by red, swollen, painful and hot skin on the extremities, mostly occurring in both feet. In 1995, Prof. Wang Jiagang defined a type of erythromelalgia with epidemic characteristics, which mainly occurred in southern China, as idiopathic erythromelalgia. 5. Congenital sensory neuropathy Congenital sensory neuropathy is a group of diseases with various clinical manifestations and easy to be confused. It is related to heredity. It is autosomal dominant. The pathogenesis is uncertain. Recurrent extremity ulcers that begin at birth, hand and foot ulcers often develop as a result of nutritional disorders and repeated injuries. The extremities are hyperalgesic and tactile. There is no specific treatment available.