If there is localized petechial hemorrhage on the leg and pressure pain on the leg, then the patient may suspect trauma-induced bruising on the leg. In addition, in the absence of a history of trauma, the patient may also be considered to have idiopathic thrombocytopenic purpura, at which point it is recommended to seek medical attention to determine the cause. When the platelets are excessively destroyed and the immune system is deficient, it will lead to bleeding in the skin mucosa, showing scattered petechiae, petechiae, which usually do not protrude from the skin surface, do not fade when pressed, and are not obviously painful to touch. Idiopathic thrombocytopenic purpura occurs in the lower extremities, mainly in the outer calves, and is often preceded by prodromal symptoms such as upper respiratory tract infection, low-grade fever, and general malaise, followed by an erythematous rash that expands into purpura within 24 hours. Idiopathic thrombocytopenic purpura is mostly self-limiting and most recover within six months. However, adult idiopathic thrombocytopenic purpura is often a chronic disease, a few of which can heal spontaneously, often with recurrent attacks. Treatment is based on controlling bleeding, and prednisone can be given for short-term treatment, and symptoms can be improved. In addition, patients with primary diseases such as cirrhosis of liver function, due to reduced platelet production, can also be seen with cyanotic plaques on the legs, and active treatment for the primary disease is recommended.