Excerpt:

Acrodermatitis chronica atrophicans (ACA) is the third or late stage of European Lyme borreliosis (LB). This unusual, progressive, fibrosing skin process is due to the effect of continuing active infection with Borrelia afzelii. Buchwald first delineated it in 1883; Herxheimer and Hartmann described it in 1902 as a tissue paper–like cutaneous atrophy. It is evident on the extremities, particularly on the extensor surfaces, beginning with an inflammatory stage with bluish red discoloration and cutaneous swelling and concluding several months or years later with an atrophic phase. Sclerotic skin plaques may also develop. Physicians should use serologic and histologic examination to confirm this diagnosis.

Pathophysiology: B afzelii is the predominant, but may not be the exclusive, etiologic agent of ACA. Another genospecies of the Borrelia burgdorferi sensu lato complex, Borrelia garinii, has also been detected.

ACA is the only form of LB in which no spontaneous remission occurs. Its pathophysiology is not yet fully understood. ACA appears to be associated with long-term persistence of Borrelia organisms in the skin; several nonspecific reactions together with a specific immune response may contribute to its manifestations.

The persistence of the spirochetes despite a marked cutaneous T-cell infiltration and high serum antibody titers may be connected with resistance of the pathogen to the complement system; the ability to escape to immunologically protected sites (eg, endothelial cells, fibroblasts); and the ability to change antigens, which may lead to an inappropriate immune response. Lack of protective antibodies, with a narrow antibody spectrum and a weak cellular response with down-regulation of major histocompatibility system class II molecules on Langerhans cells, has been observed in patients with LB.