"There is no gold standard for the diagnosis of this condition, which is often associated with preceding trauma, systemic inflammation or malignancy ref."
"The eruption initially appears as a pustule, which enlarges and ulcerates with ill-defined, undermined borders that are bluish or violaceous in colour. The surrounding skin also becomes oedematous. Secondary bacterial infection also occurs with the ulcer becoming purulent. The ulcers are typically painful. Most commonly, they occur over the pretibial region; any skin surface can be affected. Rarely, mucous membrane and airway involvement can occur."
"Iatrogenic cases have also been reported following medication use (e.g. propylthiouracil, pegfilgastrim)."