Acute Pyogenic Ankle Monoarthritis Due to Tuberculosis: A Real-Life Clinical Conundrum

Musculoskeletal tuberculosis (TB) usually involves the spine, hip, or knee. Ankle disease is rare and can present insidiously, which contributes to delayed diagnosis and poor outcomes. We report a case of an 86-year-old Chinese woman who presented with acute pain and swelling of her left ankle for two days, fevers and inability to bear weight. Past medical history included ischemic heart disease, congestive cardiac failure and recurrent urinary tract infections. Examination revealed a fever of 39.5°C and a tender, swollen ankle with restricted movement. Laboratory tests showed anaemia, lymphopenia and elevated C-reactive protein. Ankle X-ray was unremarkable. Joint aspiration yielded pus, but cultures were negative. Despite intravenous antibiotics, her symptoms persisted. MRI demonstrated marked ankle synovitis, and joint washout revealed pus around the ankle and flexor tendons. She subsequently became hypoxic, and chest imaging suggested possible miliary TB. Retrospective analysis of the aspirate confirmed acid-fast bacilli and TB polymerase chain reaction (PCR) positivity. Anti-tuberculous therapy (ATT) was commenced, but the patient deteriorated and died on day 19 of admission. This case highlights the diagnostic challenge of ankle TB, which may present acutely and mimic septic arthritis. Delayed recognition contributes to poor outcomes, and pulmonary involvement can provide important diagnostic clues. TB should be considered in the differential diagnosis of acute monoarthritis, particularly in high-risk individuals. Early recognition and prompt initiation of therapy are critical to improving patient outcomes.