Blue toe syndrome, also known as trash foot or purple toe syndrome, is caused by a blockage of the small blood vessels in the foot that reduces the flow of blood and oxygen to the tissues. It usually develops due to a problem higher up the blood stream such as an aneurysm or atherosclerosis.
The condition develops suddenly and can be really painful. It may affect one toe or a number of toes. The toes turn a blue color due to the lack of oxygen and if left untreated the skin can ulcerate, tissues begin to die and eventually gangrene sets in. If this happens, amputation may be necessary so early treatment is essential.