These ulcers are associated with ‘erythrocyanosis frigida’, which is an exclusive disease of young women. These patients have thick ankles with abnormal amount of subcutaneous fat, combined with an abnormally poor arterial supply to the ankle skin.
The blood supply of the lower third of the leg and ankle are derived from a number of fine perforating arteries arising from the posterior tibial and peroneal arteries. In erythrocyanoid cases these arteries may be abnormally small or even absent causing low grade ischemia of the whole ankle region.
When the weather is cold, the ankle is blue, cold and often tender. In hot weather chronic reactive hyperaemia becomes evident with ankle becomes hot, oedematous, swollen and painful.
Palpation of the leg will reveal small, superficial and painful nodules which breakdown to form ulcers. These ulcers are small and multiple.
Acute fat necrosis sometimes occurs on the back and outer side of the ankle, particularly with chronic exposure to cold environment. This may ultimately lead to very chronic painful ulcers. Sympathectomy may be necessary to treat such ulcer.