A clinical, histological, and immunohistochemical comparison of acrodermatitis chronica atrophicans and morphea.

We compared 19 patients with acrodermatitis chronica atrophicans (ACA), a dermatosis caused by Borrelia burgdorferi infection, and 40 patients with morphea, a disease of heterogeneous origin where a borrelia etiology has been suggested in some cases, both clinically and histologically to define the differences between these two dermatoses. Clinically, ACA involves acral body sites with lower temperatures, is seen mostly in elderly persons, and presents as a livid discoloration that is not sharply demarcated. Morphea can be localized in embryonal structures, affects any age and body site, and exhibits extension at the periphery of the lesions. Histologically, ACA shows atrophy of collagen and elastic tissue as well as hypertrophic basophilic elastic tissue; whereas in morphea, sclerosis and polarizing elastic tissue are prominent. Graft-versus-host-like reactions may be present in both dermatoses. Immunohistochemical testing with different lymphocyte markers showed differences only in the expression of HLA-DR antigens. These conditions can be distinguished from each other on a clinical and histological basis in most cases. In 17% of morphea biopsy specimens, however, histological differentiation from ACA was not possible. Moreover, the histological pattern of morphea was not associated with a positive borrelia serology.