In a retrospective study, cases of PR were retrieved from the archives of the Dermatologikum Hamburg from 1998-2005. The criteria for inclusion were an unequivocal diagnosis of PR based on clinicopathological correlation and follow up.

Thirty-four patients were included in the study. All cases were assessed regarding a variety of clinical findings including age and sex of patients, duration of lesions prior to consultation, preceding herald patch, distribution of lesions, associated symptoms, laboratory findings, course of the disease and clinical differential diagnoses.

Sections stained with H&E were reviewed independently by two of the authors (J.D. and A.B.). A minimum of four sections in each case were examined prior to grading of findings. Criteria were employed according to A. B. Ackerman's book Histologic Diagnosis of Inflammatory Skin Diseases, 3rd ed. [11] For purposes of comparison we assessed 26 of cases of seborrheic dermatitis and 29 cases of allergic contact dermatitis.

For immunohistochemistry, tissue sections were stained with the following antibodies: CD3, CD20, CD4, CD8, CD68, Cd1a, CK 16, Bcl 2, and Ki67. All slides were lightly counterstained with hematoxylin. Two authors (J.D and A.B) performed a quantitative analysis independently. At least five randomly selected high-power (X 400) fields, including the epidermis and dermis, were examined. The CD markers were evaluated based on expression pattern of positive or negative. Percentages of mononuclear cells labeled with each antibody were estimated by each observer and averaged. CK 16, Bcl 2 and Ki67 were evaluated according to expression of either positive or negative, which could be focal or diffuse when present only in some areas, or when confluent throughout the epidermis. As to the location of expression, it was defined as the upper portion of the Malphigi layer (entire upper half of Malphigi to the last cell below the horny layer) and lower portion of the Malphigi layer (all the lower half of Malpighi including or excluding the suprabasal cells).