Climatotherapy at the Dead Sea is a remittive therapy for psoriasis: Combined effects on epidermal and immunologic activation

Background: The beneficial effect of climatotherapy at the Dead Sea (CDS) for psoriasis has been established clinically but there is a striking lack of studies assessing its in vivo effect at the molecular and cellular levels. Objective: We sought to study the response of activated immunologic cells and keratinocytes in psoriatic lesions to CDS. Methods: A total of 27 patients with chronic, stable, plaque-type psoriasis treated with CDS for 28 consecutive days were evaluated with the Psoriasis Area and Severity Index score and quantitative histologic measures. Results: After 4 weeks of treatment, the overall Psoriasis Area and Severity Index score decreased by 81.5%. Complete clearance was achieved in 48% of the patients, and moderate to marked improvement in 41%. The average duration of remission was 3.3 months. Histologically, there was an overall reduction in malpighian layer thickness by 63.4%, and keratinocyte hyperplasia, assessed by Ki-67 cell cycle antigen expression, decreased by 78%; residual cell proliferation was confined mainly to the basal layer. These changes were accompanied by normalization of keratin 16 expression in 90% of the patients. T lymphocytes were almost totally eliminated from the epidermis (depletion of >90% of CD3⁺ and CD25⁺ cells), with only a low number remaining in the dermis (depletion of 69.4% of CD3⁺ cells and 77.4% of CD25⁺ cells). This reduction in activated T cells was accompanied by a marked reduction in HLA-DR expression by epidermal keratinocytes. Conclusions: CDS is a highly effective and remittive treatment for moderate to severe plaque-type psoriasis, leading to a reversal of both pathologic epidermal and immunologic activation.