The amber theory of Lyme arthritis: initial description and clinical implications.

Lyme arthritis differs in many respects from other bacterial causes of arthritis. Based on an observation made for a patient with Lyme arthritis, we propose that the pathogenesis of joint swelling in Lyme arthritis is due to the introduction into the joint space of non-viable spirochetes or more likely spirochetal debris enmeshed in a host-derived fibrinous or collagenous matrix. This "amber" hypothesis can account for the clinical and laboratory features of Lyme arthritis and is amenable to experimental validation. Validation would directly impact the clinical management of patients with Lyme arthritis.