Purple plaque appears on the leg for no reason. Purpura should be considered, which is subcutaneous congestion plaque. There are several possibilities for this situation: first, many normal women's blood coagulation function decreases before menstruation, which can lead to scattered ecchymosis on the trunk or limbs. Second, factors such as collision, trauma or local compression can cause subcutaneous capillary rupture and bleeding, leading to ecchymosis. Third, some old people's capillaries are brittle, and there will be flaky ecchymosis. In addition to the above common factors, some diseases in the body can also lead to ecchymosis, such as thrombocytopenia, renal failure, abnormal coagulation function, hemophilia and so on. If there is no history of trauma, subcutaneous ecchymosis will gradually increase and increase. In this case, it is recommended to go to the hospital for some tests to rule out the possibility of the above diseases.