Case Report: Foreign Body-induced Pseudomonas Arthritis Mimicking Tuberculous Ankle Infection in a Child.

Introduction: Pediatric osteoarticular infections often present diagnostic challenges, especially in regions endemic to tuberculosis (TB). Misinterpretation of imaging findings may lead to inappropriate treatment, including the unwarranted use of anti-tubercular therapy (ATT). Case Report: We present the case of a 10-year-old child with chronic left ankle swelling and pain for over a year, initially diagnosed with tuberculous arthritis based on magnetic resonance imaging findings. Despite 2 months of ATT, symptoms persisted. Upon referral, further evaluation, including biopsy and culture, revealed a retained foreign body (thorn) within the ankle joint capsule and Pseudomonas aeruginosa infection. ATT was discontinued, and antibiotic therapy, as per culture sensitivity, was initiated, leading to complete clinical recovery. Conclusion: This case underscores the importance of microbiological or histopathological confirmation before initiating ATT in osteoarticular infections. Reliance solely on imaging may lead to misdiagnosis, delayed appropriate treatment, and potential public health implications. Clinicians should maintain a high index of suspicion for alternative diagnoses, especially in atypical presentations or non-responders to ATT.