Scrub Typhus-Associated Inflammatory Oligoarthritis Mimicking Tubercular Arthritis in an Endemic Setting.

Scrub typhus is a common cause of acute febrile illness in endemic regions; however, musculoskeletal involvement is usually limited to myalgia, and true inflammatory arthritis is rarely reported. We describe a 19-year-old previously healthy male military recruit who presented with a two-month history of progressive bilateral knee swelling and left ankle pain, accompanied by fever, weight loss, and lymphadenopathy. Clinical evaluation revealed inflammatory oligoarthritis with culture-negative synovial fluid. Given the chronicity of symptoms and systemic features, tubercular and septic arthritis were initially considered. Imaging showed preserved joint architecture, and synovial fluid analysis demonstrated inflammatory features without microbial growth. Investigations for tuberculosis, autoimmune disorders, and other tropical infections were negative. Serological testing was positive for scrub typhus immunoglobulin M using a rapid immunochromatographic assay. Following the initiation of doxycycline therapy, the patient showed rapid clinical improvement with resolution of fever and marked reduction in joint symptoms. This case highlights an uncommon presentation of scrub typhus-associated inflammatory oligoarthritis mimicking tubercular arthritis in endemic regions. Clinicians should consider scrub typhus in patients presenting with febrile oligoarthritis and culture-negative joint effusion, as early recognition and appropriate treatment can result in excellent outcomes.