Fever, Diarrhea, and Weight Loss in a Man With Inflammatory Polyarthritis

A 61-year-old man with seronegative rheumatoid arthritis had persistent polyarthralgias, fever, and unintentional weight loss with an elevated CRP level despite treatment; he also had intermittent abdominal pain, protein-losing enteropathy, and steatorrhea, and esophagogastroduodenoscopy findings of white duodenal plaques with biopsy showing macrophages in the duodenal mucosa. What is the diagnosis and what would you do next?
Source: JAMA - Journal of the American Medical Association - Category: General Medicine Source Type: research