Adult-Onset Still Disease Triggered by Recent Cytomegalovirus Infection: A Diagnosis of Exclusion and a Review of the Literature.

Adult-onset Still disease (AOSD) is a rare systemic autoinflammatory disorder characterized by quotidian fever, inflammatory arthritis, evanescent rash, neutrophilic leukocytosis, and hyperferritinemia. Because no pathognomonic diagnostic test exists, diagnosis relies on characteristic clinical features and exclusion of infectious, malignant, and autoimmune disorders. Viral infections, including cytomegalovirus (CMV), have been proposed as potential immunologic triggers in genetically susceptible individuals, although causality remains unproven. We report a 47-year-old Hispanic woman with hypertension and type 2 diabetes mellitus who presented with one week of daily fever, severe diffuse polyarthralgia, sore throat, fatigue, and a persistent erythematous rash that had begun six months earlier. Laboratory evaluation revealed marked neutrophilic leukocytosis (27.3 × 109/L), hyperferritinemia (2,853 ng/mL), elevated erythrocyte sedimentation rate (110 mm/hour), C-reactive protein (26 mg/dL), and procalcitonin (5.84 ng/mL). Extensive infectious evaluation, including blood cultures and testing for HIV, Epstein-Barr virus, tick-borne diseases, sexually transmitted infections, and other pathogens, was negative except for positive CMV IgG and IgM. Comprehensive autoimmune testing, peripheral blood smear, and computed tomography excluded connective tissue disease and hematologic malignancy. After systematic exclusion of alternative diagnoses, the patient fulfilled Yamaguchi criteria for AOSD. Prednisone 40 mg daily resulted in rapid resolution of fever, improvement in arthralgia, and normalization of inflammatory markers. This case highlights the diagnostic complexity of AOSD and suggests that recent CMV infection may act as an immunologic trigger rather than the primary disease process.