IL-36a and IL-36y expressions in the differential diagnosis of palmoplantar psoriasis and palmoplantar eczema: A retrospective histopathologic and immunohistochemical study

Abstract

Background: Diagnosing hyperkeratotic lesions on the palms and soles is often challenging for both clinicians and pathologists. Interleukin (IL)-36 cytokines play an important role in the pathogenesis of psoriasis. Methods: We retrospectively re-evaluated hematoxylin-eosin-stained biopsy specimens of 30 patients with clinically diagnosed palmoplantar psoriasis (PP) and 30 patients with palmoplantar eczema (PE), and then performed IL-36a and IL-36y immunohistochemistry. Results: Among the histopathologic features, thinning of the rete ridges and vertical alternation of parakeratosis and orthokeratosis had the highest positive predictive value (PPV) in diagnosing PP (72.7% and 69.3%, respectively). Immunohistochemically, patients with PP predominantly showed diffuse or focal strong expression with IL-36a and IL-36y staining in the upper layers of the epidermis (86.7% and 83.3%, respectively). The comparison of the mean IL-36a and IL-36y expression scores significantly differed between PP and PE (P < .001). Among all histopathologic and immunohistochemical features, diffuse strong expression of IL-36a and IL-36y staining had the highest PPVs in favor of a diagnosis of PP (75% and 76.7%, respectively). Conclusions: Our data suggest that IL-36a and IL-36y immunohistochemistry can be used in the differential diagnosis of PP and PE.