Skin petechiae are hemorrhagic patchy lesions of the skin and mucous membranes, the nature of which is the same as bleeding spots, mostly suggesting hematological disorders or diseases causing bleeding and clotting abnormalities. Examination: 1, vascular purpura: very common, due to damage of blood vessel wall or its increased fragility and permeability, common in immune (such as allergic purpura), infectious (such as sepsis), abnormal vascular structure (such as hereditary hemorrhagic capillary dilatation) and other (such as abnormal proteinemia, simple or senile purpura, etc.) diseases. The examination is not abnormal except for the bundle arm test which may be positive. 2, abnormal platelet purpura: the most common, mostly due to platelet reduction, increase and abnormal function, if there is purpura or blood blister in oral cheek mucosa, it often indicates serious bleeding and should be actively treated. 3, coagulation mechanism disorders: including coagulation factor deficiency, circulating anticoagulant substances or fibrinolytic hyperactivity, generally speaking, bleeding caused by coagulation mechanism disorders, mainly manifested as joint hematoma, muscle hematoma and visceral bleeding, less manifested skin purpura, only sometimes manifested as large petechiae, and check coagulation signs have obvious abnormalities, so that can be distinguished from vascular purpura and purpura caused by platelet abnormalities. The treatment of purpura varies depending on the cause.