Purpura is a bleeding disorder caused by abnormalities in the walls of blood vessels and surrounding tissues, and is a manifestation caused by blood cells entering the skin or subcutaneous tissues. The causes of purpura are as follows: 1, reduced platelet count: seen in primary and secondary thrombocytopenic purpura, thrombotic thrombocytopenic purpura, etc.; 2, abnormal platelet function: seen in giant platelet syndrome, platelet anemia, platelet type vascular hemophilia, etc.; 3, coagulation factor deficiency: seen in disseminated intravascular coagulation, hemophilia, etc.; vascular abnormalities can also cause purpura. The causes are: 1, increased vascular transmural pressure: such as violent cough, straining during childbirth, venous stasis, etc.; 2, vascular damage: such as damage to blood vessels by ultraviolet radiation, infection, embolism, allergy, inflammation, tumors, poisoning, drug-related factors; 3, reduced integrity of microcirculation and vascular support tissues: such as age-related purpura, connective tissue abnormalities, overuse of glucocorticoids, vitamin C deficiency, amyloid infiltration, etc. There are many causes of purpura, clinically, for patients with purpura, they should actively search and treat the primary disease in order to fundamentally improve the symptoms of purpura, but these diseases are prone to recurrence, patients diagnosed should be actively treated and followed up.