Immunohistochemical Expression of Ki-67 and Epidermal Thickness in Psoriasis Vulgaris: A Comparative Study with Healthy Controls

Leen N. Almohammadi, Yusra O. Zakaria, Faris Elmahdi

Abstract: Background: Psoriasis vulgaris is a chronic immune-mediated skin disease marked by keratinocyte hyperproliferation. Ki-67 is a nuclear proliferation marker widely used to quantify this activity. Data on Ki-67 expression and epidermal thickness in Saudi patients are limited. Objective: To compare Ki-67 immunohistochemical positivity and epidermal thickness between patients with psoriasis vulgaris and healthy controls. Methods: This retrospective comparative cross-sectional study included 50 patients with histologically confirmed psoriasis vulgaris and 50 controls from multiple hospitals in Saudi Arabia, between May 2024 and May 2025. Skin biopsies were stained with hematoxylin and eosin and immunohistochemically for Ki-67. Epidermal thickness was measured in micrometres. Groups were compared using the chi-square test and the independent-samples t-test. Results: The groups were comparable in sex distribution (males 66.0% vs. 60.0%; P = 0.534). Among patients, disease was mild in 20.0%, moderate in 38.0% and severe in 42.0%. Ki-67 positivity was higher in psoriasis than in controls (60.0% vs. 40.0%; P = 0.046). Mean epidermal thickness was 43.1 ± 32.7 µm in psoriasis and 58.3 ± 27.3 µm in controls (mean difference -15.2 µm; 95% CI -27.2 to -3.2; P = 0.013). Conclusions: Ki-67 positivity was more frequent in psoriatic skin than in healthy control skin, although statistical significance depended on the test applied. The unexpected lower epidermal thickness in the psoriasis group requires verification of the original measurements and sampling procedures. Further studies using quantitative Ki-67 indices and standardized epidermal measurements are recommended.

Keywords: psoriasis vulgaris, Ki-67 antigen, immunohistochemistry, epidermal thickness, keratinocyte proliferation, Saudi Arabia