Dental metal hypersensitivity in patients with psoriasis vulgaris: A case‐control study using an in vitro quantitative sensitivity test

Abstract

The etiology of psoriasis is not fully understood, even though several genetic and environmental contributing factors have been suspected. Evidence has accumulated that pathological autoimmune responses mediated via the IL-23/IL-17 axis underlie psoriatic skin inflammation. Similar dermal activation of the Th17 immunity has also been observed in patients with metal hypersensitivity. Metal hypersensitivity involves a T cell-mediated, delayed-type hypersensitivity reaction that causes local contact dermatitis and systemic cutaneous inflammation and is closely associated with a subset of inflammatory autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, and Sjögren s syndrome. In addition, hypersensitivity to dental metals strongly correlates with cutaneous inflammatory conditions such as palmoplantar pustulosis, lichen planus, and dyshidrotic eczema. These facts prompted us to assess the contribution of dental metal hypersensitivity to psoriasis. We conducted a case-control retrospective study of the prevalence of hypersensitivity to zinc, gold, nickel, and palladium, which are the metals commonly used for dental alloys. A total of 53 Japanese patients with psoriasis vulgaris (PV) and 22 ageand sex-matched healthy controls (HC) were enrolled (PV: 20 males and 33 females, age range 22-83 years, mean age [SD] 50.2 [14.4] years; HC: 7 males and 15 females, ages 12-70 years, mean age [SD] 48.9 [13.7] years). All subjects were users of metallic dental implants and/or prostheses containing zinc, gold, nickel, and/or palladium as major constituents. Written informed consent was obtained from each participant. We employed the lymphocyte transformation test (LTT) to evaluate the sensitivity to the metals quantitatively. LTT was outsourced to SRL, Inc. (Tokyo, Japan). The stimulation index (SI) was calculated as SI = 100 × (cpm of [H]thymidine incorporated into peripheral blood lymphocytes during stimulation with a metal species/cpm without stimulation). Any subject with an SI value of ≥180 was regarded as hypersensitive according to previous studies. The majority of HC individuals (68.2%) were negative for sensitivity to any metals examined, and the rest (31.8%) were hypersensitive to only a single metal species (Figure 1A). In contrast, half (52.8%) of PV patients were hypersensitive to at least one metal species, and 30.2% were hypersensitive to more than one species. However, we found no significant difference in the overall prevalence of metal hypersensitivity between PV and HC (P = .129; odds ratio = 0.420; 95% confidence interval = 0.150-1.19; Figure 1A). Furthermore, there was no significant difference in the prevalence of hypersensitivity to individual metals between PV and HC (Figure 1B). No significant difference was also observed in the mean SI value of each metal between PV and HC (Figure 1B). The prevalence of metal sensitization in patients with psoriasis has been investigated in patch test studies, yielding controversial results. Some of the previous studies have demonstrated that patients with psoriasis have a significantly lower prevalence of metal hypersensitivity than healthy individuals, but others have shown comparable prevalence between psoriasis patients and healthy controls. Our result from an in vitro LTT study supports Received: 24 June 2020 Revised: 16 November 2020 Accepted: 27 November 2020