S6107 Cytomegalovirus Duodenitis Mimicking Malignancy: First Reported Case of Obstructive Pseudotumor in CVID Treated Endoscopically

Introduction: Cytomegalovirus gastrointestinal (GI) infection is common in immunocompromised patients, but isolated cytomegalovirus pseudotumors are rare, with <25 cases reported. Most involve the colon (∼40%), stomach (∼20%), and other GI sites, duodenal involvement is extremely rare (<1%). This is the first reported case of cytomegalovirus duodenitis pseudotumor in a common variable immunodeficiency (CVID) patient. Case Description/Methods: A 66-year-old man with CVID and cirrhosis underwent screening esophagogastroduodenoscopy, revealing a fungating duodenal mass due to cytomegalovirus duodenitis, treated with ganciclovir. A month later, he presented with vomiting, dysphagia, weight loss & elevated liver function tests (LFTs) (AST 65, ALT 74, ALP 552, TBili 1.1). Computed tomography showed a CBD filling defect and duodenal mass with omental caking (biopsy negative for malignancy). LFTs worsened (AST 326, ALT 217, ALP 1487, TBili 26). Magnetic resonance cholangiopancreatography deferred due to claustrophobia. Liver biopsy revealed interface hepatitis, likely viral or drug-induced liver injury. Tumor markers, hepatitis panel, and AMA were negative, cytomegalovirus viremia also ruled out. Esophagogastroduodenoscopy (EGD) showed duodenal ulceration with high-grade narrowing. Balloon dilation to 13.5 mm disrupted the stricture, but the scope could not pass. Biopsies confirmed cytomegalovirus duodenitis. He received ganciclovir/valganciclovir for 4 weeks, with mild improvement in symptoms and LFTs. A month later, EGD showed persistent stricture, lumen apposing metal stent (LAMS) was placed. At follow-up, mild narrowing remained, prompting a second LAMS. Three months later, EGD showed stricture improvement, and the stent was removed. At follow-up, his symptoms resolved and LFTs normalized. Discussion: cytomegalovirus duodenitis can cause ulceration, bleeding, perforation, pseudotumor, strictures, fistulas, malabsorption, and cholestatic liver injury. Our patient with CVID and cirrhosis developed obstructive symptoms and cholestatic LFT elevation due to cytomegalovirus duodenitis mimicking malignancy. Cytomegalovirus pseudotumors are inflammatory, mass-like lesions with granulation tissue and viral inclusions. He had high-grade duodenal narrowing with bile duct compression. Diagnosis was challenging due to nonspecific imaging and endoscopic findings. Omental caking and persistent stricture raised concern for malignancy, but repeat biopsies confirmed cytomegalovirus. Negative cytomegalovirus polymerase chain reaction highlighted the importance of tissue biopsy and immunohistochemistry. He required serial dilations and LAMS placements. While most cytomegalovirus duodenitis cases respond to antivirals alone, this rare duodenal pseudotumor is the first reported to be successfully treated with combined antiviral and advanced endoscopic therapy, avoiding surgery and achieving full clinical resolution.