A 76-year-old white woman was referred to the dermatology clinic for evaluation of a week-long pruritic rash that had begun on her legs and had progressed to the groin area. Her medical history was significant for asthma, whichhad been diagnosed 2 years earlier. She stated that the asthma symptoms had recently improved, coinciding with the onset of the rash. She also complained of a 10- to 15-year history of numbness and occasional pain in her left toes. She reported an unintentional 5-kg weight loss in the preceding year. She had been hospitalized the year before because of several episodes of diarrhea and pneumonia. Previous laboratory studies were significant for leukocytosis and eosinophilia as high as 55%.