Gastroenterology clinical image challenge: A 55-year-old man presented with a two-week history of acute-onset diarrhea characterized by the passage of multiple, explosive, watery, nonbloody bowel movements per day after attending the state fair. The patient’s past medical history was significant for Waldenstrom macroglobulinemia status post autologous stem cell transplantation and splenectomy three and seven years ago, respectively. Owing to autoimmune hemolytic anemia, repeat autologous stem cell transplantation and initiation of chronic immunosuppression therapy was started three months before presentation. Current medications included cyclosporine and prednisone 50 mg orally once daily along with prophylactic acyclovir, fluconazole and trimethoprim-sulfamethoxazole.
Physical examination was notable for Cushingoid features and dry mucous membranes; abdominal examination and vital signs were unremarkable. Stool studies for bacterial enteric pathogens, Clostridium difficile toxin polymerase chain reaction (PCR), ova and parasites, Cryptosporidium/Cyclospora antigens (Ag), Giardia Ag, and Rotavirus Ag. Blood testing for cytomegalovirus (CMV) PCR and human immunodeficiency virus were negative. A 48-hour stool collection revealed a total stool weight of 2317 g and 39 g of fat/24 hours (normal, 2-7 g/24 hours). Computed tomographic enterography demonstrated a normal-appearing small bowel, evidence of prior splenectomy and bilateral lower lobe pulmonary nodules measuring up to 1 cm in diameter. Upper endoscopy revealed several nodular antral erosions, but was otherwise unremarkable. Biopsies from the gastric erosions and duodenum demonstrated enlarged nuclei with “smudgy” chromatin and intranuclear inclusions on hematoxylin and eosin staining (Figure). CMV immunostaining was negative. Colonoscopy showed normal-appearing colonic and ileal mucosa and corresponding random biopsies including Congo red, CMV, and herpes simplex virus immunostains were normal.
What is the most likely diagnosis based on the clinical presentation, endoscopic description, and histologic findings?
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