Background: Chronic actinic dermatitis (CAD) is a recurrent photosensitive dermatitis that occurs predominantly on sun-exposed areas with unknown etiology. In severe cases, it may present with erythroderma, which is clinicopathologically analogous to cutaneous T-cell lymphoma. Typically, inflammatory infiltrates in the skin lesions are mainly CD8+ reactive T cells. However, hematologic characteristics of CAD have not been fully elucidated. Methods: Twenty patients with CAD ranging in age from 45 to 86 years (median, 64), including 17 males and three females (M/F ratio, 5.7), were examined. All patients were phototested for UV light. In addition, seven of the 20 patients with extensive eruption were also tested for visible light. All biopsy specimens were obtained from the CAD eruptions (n = 25 lesions). Histopathologic and immunohistochemical studies were performed. Furthermore, flow cytometric analysis was performed to determine the CD4/8 ratio using peripheral blood mononuclear cells of 13 of the 20 patients. Results: In 11 of the 20 patients (55%), the eruption was localized to sun-exposed areas. Skin-infiltrating T cells were CD8-dominant in the CAD eruption. Three patients (15%) showed erythroderma with a reduced CD4/8 ratio (median, 0.7) of peripheral mononuclear cells. As for treatment, eight of the 20 patients (40%) required oral cyclosporine in addition to topical therapies. Subsequently, the reduced CD4/8 ratio was normalized after treatment in two of the three patients with erythroderma. Conclusions: We considered that there appeared to be a relationship between the reduced CD4/8 ratio of circulating T cells (hematologic burden) and the affected area (skin burden).
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