Cytomegalovirus Gastrointestinal Disease Masquerading as Inflammatory Bowel Disease in a Patient with Occult HIV Infection Receiving Biologics: A Case Report.

INTRODUCTION: Biologic and targeted synthetic therapies can obscure underlying immunodeficiency and opportunistic infections, leading to diagnostic challenges in patients with presumed autoimmune disease. CASE PRESENTATION: A 51-year-old man with ankylosing spondylitis and presumed ulcerative colitis experienced progressive systemic decline, including 40 lb. weight loss and encephalopathy, while receiving etanercept and upadacitinib. Clinical deterioration prompted reassessment, revealing advanced HIV/AIDS (CD4 count 21 cells/µL) and biopsy-confirmed cytomegalovirus esophagitis. Discontinuation of Janus kinase inhibition and initiation of antiretroviral therapy resulted in clinical stabilization. CONCLUSION: This case highlights the dangers of diagnostic momentum and demonstrates how opportunistic infections can mimic autoimmune pathology, emphasizing the need for diagnostic reassessment and objectivity in patients receiving potent immunomodulatory therapies.