Abdominal Pain and Petechial Rash in a 95-Year-Old Farmer

A 95-year-old farmer taking prednisolone for bullous pemphigoid had 24 hours of abdominal pain, 2 weeks of diarrhea, and 3 months of intermittent abdominal bloating and anorexia. Evaluation showed purpuric macules and small thumbprint-like patches on her upper abdomen and central chest and a white blood cell count of 13 600/μL (89.9% neutrophils, 0.2% eosinophils). What is the diagnosis and what would you do next?