Lupus erythematosus causes vasculitis, and vasculitis is a common pathological change in lupus erythematosus. In general, a large number of petechiae can be seen on both hands and feet, and reticular cyanosis and lamellar cyanosis can be seen on both legs, which are usually vasculitis caused by lupus erythematosus. The principle is that a large number of immune complexes block tiny blood vessels, causing embolic small-vessel vasculitis and terminal necrotic small-vessel vasculitis, which may cause indurated ulcers or necrosis at the fingertips when the symptoms are severe.