Allergic Contact Dermatitis in Psoriasis Patients: Typical, Delayed, and Non-Interacting

Abstract

Psoriasis is characterized by an apoptosis-resistant and metabolic active epidermis, while a hallmark for allergic contact dermatitis (ACD) is T cell-induced keratinocyte apoptosis. Here, we induced ACD reactions in psoriasis patients sensitized to nickel (n = 14) to investigate underlying mechanisms of psoriasis and ACD simultaneously. All patients developed a clinically and histologically typical dermatitis upon nickel challenge even in close proximity to pre-existing psoriasis plaques. However, the ACD reaction was delayed as compared to non-psoriatic patients, with a maximum intensity after 7 days. Whole genome expression analysis revealed alterations in numerous pathways related to metabolism and proliferation in non-involved skin of psoriasis patients as compared to non-psoriatic individuals, indicating that even in clinically non-involved skin of psoriasis patients molecular events opposing contact dermatitis may occur. Immunohistochemical comparison of ACD reactions as well as in vitro secretion analysis of lesional T cells showed a higher Th17 and neutrophilic migration as well as epidermal proliferation in psoriasis, while ACD reactions were dominated by cytotoxic CD8+ T cells and a Th2 signature. Based on these findings, we hypothesized an ACD reaction directly on top of a pre-existing psoriasis plaque might influence the clinical course of psoriasis. We observed a strong clinical inflammation with a mixed psoriasis and eczema phenotype in histology. Surprisingly, the initial psoriasis plaque was unaltered after self-limitation of the ACD reaction. We conclude that sensitized psoriasis patients develop a typical, but delayed ACD reaction which might be relevant for patch test evaluation in clinical practice. Psoriasis and ACD are driven by distinct and independent immune mechanisms.

Hand dermatitis – differential diagnoses, diagnostics, and treatment options

“…In psoriasis patients, a delayed onset of positive patch test reactions has been observed (only after 7 days). Thus, besides usual readings after 48 and 72 hours, another patch test reading after 7 days appears necessary in this patient group .…”

Patch testing in patients with psoriasis: results of a 30-year retrospective study

“…To dissect the immunological overlap between ACD and psoriasis, one group analysed the effect of patch testing on psoriatic plaques in patients with known nickel sensitivity . They found that the ACD reaction was typical with a maximum intensity after 7 days and that allergen challenge did not affect the appearance of the underlying psoriatic plaque (as graded by the local Psoriasis Area and Severity Index score).…”

A Case of Psoriasis Replaced by Allergic Contact Dermatitis in a 12‐Year‐Old Boy

“…Psoriasis and ACD are distinct disease entities that share an immune‐mediated pathogenesis. In our patient, we suspect that the immunologic response to a hapten in lavender oil disrupted the Th1 pathogenesis of psoriasis, shifting to a Th2 immune response and leading to the apparent remission of the psoriasis . Although most agree that the skin barrier dysfunction in psoriasis eases entry of allergens, a review of the literature suggests that the relationship between psoriasis and ACD remains unclear.…”