Leg hair suddenly bald piece, in the clinic may be seen in limited patchy baldness, ringworm and purulent folliculitis and other factors. 1. limited patchy baldness is one of the more common types of baldness, because the lesion only occurs in a limited area, and the border is clearer, so it is also called limited patchy baldness, the cause of the onset of the disease may be related to heredity, autoimmune abnormality, as well as mental anomalies and other factors. 2. Ringworm is a skin disease caused by localized skin infection with ringworm bacteria, which can damage hair follicles, so it may lead to localized hair loss. 3. Purulent folliculitis refers to widespread purulent infection on the basis of folliculitis, because the infection will cause damage to the hair follicle, so it will also cause permanent hair loss, manifested as localized hair loss. Due to the many factors affecting it, the specific situation needs to be identified by a doctor and analyzed in the context of the actual situation.