The Value of Musculoskeletal Ultrasound for Evaluation of Postinfectious Lyme Arthritis

Background Inflammatory arthritis is the most common late manifestation of untreated Lyme disease in the United States. While antimicrobial therapy is effective in resolving swelling and pain for 90% of patients, many patients have persistent inflammation, termed postinfectious Lyme arthritis (PILA). Current outcome measures for Lyme arthritis have several limitations, as improvement is considered a dichotomous outcome based solely on physical examination. There is growing interest in the use of ultrasonography to better define outcomes in inflammatory arthritis, and this is particularly relevant for conditions such as late Lyme arthritis and PILA, which are monoarticular or oligoarticular. We describe results from a series of 5 patients who underwent ultrasound evaluations leading to a diagnosis of PILA. Methods This is a case series describing 5 patients with PILA who were referred for evaluation and treatment of symptomatic joints. Results Musculoskeletal ultrasound showed significant joint pathology, even in cases with minimal clinical findings. Synovitis, effusions, enthesitis/tendinopathy, and bone erosions were seen and helped confirm the presence of ongoing inflammatory arthritis. Conclusions Marked inflammatory change - with synovitis, enthesitis and erosions - can be seen in selected patients with PILA. Systematic sonographic evaluation of patients with PILA is needed to further evaluate pathology and treatment response.