A 61-year-old white man with seronegative rheumatoid arthritis presented with hand and wrist pain. Over 2 years, he was prescribed various therapies including prednisone, methotrexate, tumor necrosis factor inhibitors, abatacept, and anakinra; he experienced intermittent improvement in his joint pain but had persistently elevated levels of inflammatory markers. He continued to experience asymmetric small-and large-joint polyarthralgias and later developed intermittent fevers (temperatures up to 38.3°C [101°F]) along with a 50-lb (22.7-kg) unintentional weight loss over the course of a few months.On examination, there was subtle synovitis in bilateral metacarpophalangeal joints. Findings on cardiac, pulmonary, and neurologic examinations were unremarkable. Laboratory evaluation was notable for a normocytic anemia and elevated C-reactive protein level (7.7 mg/dL [73.3 nmol/L]). Results of esophagogastroduodenoscopy with gastric biopsies and bone marrow biopsy were unremarkable. Findings on further workup including transthoracic echocardiography to assess for endocarditis, carotid magnetic resonance angiography to assess for vasculitis, and abdominal fat pad biopsy for amyloidosis were also unremarkable. Tocilizumab was initiated. Over the next several months, he developed intermittent abdominal pain, steatorrhea, protein-losing enteropathy, and symmetric bilateral lower extremity edema requiring diuresis. Results of infectious stool studies, celiac serology, and fecal elastase testing were normal. Repeat esophagogastroduodenoscopy (Figure , panel A) was performed, with gastric and duodenal biopsies (Figure, panels B and C).