Mycobacterium tuberculosis infectious monoarthritis in a paediatric patient.

Mycobacterium tuberculosis is uncommon in the USA, and when it is diagnosed, it is usually in adult patients with identifiable risk factors presenting with pulmonary manifestations of the disease. Paediatric tuberculosis is rare, and a minority of those cases can present with isolated extrapulmonary infection. When the musculoskeletal system is involved, there are often no constitutional symptoms, and it can resemble other infectious and inflammatory processes. Diagnosis is challenging, and delay leads to irreversible destructive osteoarticular changes. A prompt diagnosis requires a high index of suspicion. This report presents a case of successfully diagnosed paediatric M. tuberculosis monoarthritis of the knee to highlight these challenges.