Left-sided abdominal pain of 5 days' duration and the recent appearance of purplish discoloration on the abdomen prompt a 58-year-old woman to seek emergent medical care. She has also had a severe nonproductive cough for 2 months. The patient does not have diabetes, and she has not received the influenza or pneumococcal vaccines. She denies alcohol(Drug information on alcohol) use. Other physical examination findings are unremarkable.To what do you attribute the skin discoloration?