Utility of IL‐36 immunostaining in distinguishing psoriasis from pityriasis rosea and pityriasis lichenoides

Abstract

AbstractBackgroundPsoriasis is an inflammatory skin disease driven by upregulation of cytokines in the Th17 pathway, including interleukin‐36 (IL‐36). Previous studies have highlighted the utility of IL‐36 immunostaining for psoriasis compared to spongiotic dermatitis and other psoriasiform dermatoses; however, no study has examined the role of IL‐36 staining in distinguishing psoriasis from pityriasis rosea (PR) and pityriasis lichenoides (PL), known histologic mimickers of psoriasis.MethodsWe compared the immunostaining pattern of IL‐36 for 21 PR cases, 22 PL cases, and 10 psoriasis cases. We graded the immunostaining as 0, negative; 1, focal weak; 2, diffuse weak; 3, focal, strong; or 4, diffuse strong. We further categorized stains as negative (0–2 score) or positive (3–4 score) and utilized Fisher's exact test to compare the immunostaining pattern of these entities.ResultsAll psoriasis specimens were positive for IL‐36, whereas all PR specimens were negative (p = 0.00000002). Twenty PL specimens were negative (p = 0.000001). Nine of 10 pityriasis lichenoides et varioliformis acuta cases were negative (p = 0.00012), and 11 of 12 cases of pityriasis lichenoides chronica were negative (p = 0.00003).ConclusionsOur findings highlight the potential role of IL‐36 immunostaining in distinguishing psoriasis from other psoriasiform dermatoses, including PR and PL.