Case Report: When infection wears a rheumatic mask: probable systemic brucellosis mimicking seronegative inflammatory arthritis with sicca symptoms and suspected cervical spondylitis

Background Brucellosis is a zoonotic infection with protean manifestations. Osteoarticular disease is common, but presentation as seronegative inflammatory arthritis with sicca symptoms, generalized lymphadenopathy, and cervical spondylitis may be mistaken for autoimmune rheumatic disease. Case presentation A 58-year-old male cattle farmer presented with intermittent chills, sicca symptoms, symmetric polyarthritis, weight loss, anemia, hypoalbuminemia, and elevated inflammatory markers. Autoimmune serology was negative. Ultrasonography confirmed synovial hyperplasia and tenosynovitis. 18F-FDG PET/CT showed generalized lymphadenopathy and focal C5 uptake; MRI showed C5 marrow edema. Lymph-node biopsy demonstrated non-necrotizing granulomatous inflammation with negative acid-fast and periodic acid-Schiff stains. Positive Rose Bengal and Brucella IgG tests, a standard tube agglutination titer of 1:100, and the clinical context prompted a working diagnosis of probable systemic brucellosis. Blood and bone marrow cultures were negative; paired serology was unavailable. At telephone follow-up, the patient reported taking outpatient rifampicin and doxycycline for 2 years, near-resolution of cervical pain at approximately 3 months, and normalization of inflammatory markers and hemoglobin after more than 6 months. A negative local agglutination result reported by his daughter at approximately 3 months could not be verified. Intermittent bilateral hip and knee pain persisted, requiring as-needed etoricoxib and, at the latest follow-up, a walking aid. Treatment had been extended because symptoms persisted, but the cause of the functional impairment remained undetermined. Conclusion Probable systemic brucellosis merits consideration in exposed patients with seronegative inflammatory arthritis, sicca symptoms, and granulomatous lymphadenopathy. Occupational seropositivity, incomplete microbiological confirmation, and unverified follow-up testing limit diagnostic certainty. Symptomatic improvement during antibiotics does not establish the etiology or microbiological cure, and persistent disability warrants reassessment for infection, structural disease, and coexisting rheumatic pathology.