Differential diagnosis should be made with the following symptoms: 1. Red and purple skin and mucous membranes: The skin and mucous membranes protect the body, making the body a closed system to the outside world, when harmful substances will invade the body, the first is the skin and mucous membranes to block external pathogenic factors outside the body. Therefore, the skin and mucous membranes are the first line of defense against infection. But when the invasion of harmful substances exceeds the capacity of the mucous membrane, it will cause redness, swelling, discoloration and other damage to the skin and mucous membrane. 2, skin mucous membrane bleeding: caused by the body’s hemostasis or coagulation function disorders, usually systemic or limited skin mucous membrane spontaneous bleeding or difficult to stop bleeding after injury as clinical features. Visible mucosa is usually examined conjunctiva, lips, fingernails.