Comparative Immunoprofiling in Psoriasis and Psoriasiform Dermatitis Using Inflammatory and Structural Biomarkers: A Preliminary Study

Background: Differentiating psoriasis from psoriasiform dermatitis can be challenging due to overlapping clinical and morphological features, especially in certain areas, such as the palms, soles and scalp. While the distinct roles of the Th17 and Th2 axes in these inflammatory dermatoses are recognized, the comprehensive in situ expression of adhesion molecules, inflammatory cytokines, and structural markers within a unified diagnostic framework remains incompletely characterized. Objectives: The aim of this study was to compare the immunohistochemical expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-17A (IL-17A), Collagen IV, and S100B in psoriasis and psoriasiform dermatitis and to evaluate their diagnostic and pathogenetic significance. Methods: This retrospective observational study evaluated skin biopsy specimens from 22 patients: 11 with psoriasis and 11 with psoriasiform dermatitis. Immunohistochemical staining was performed for seven markers. Expression intensity was semi-quantitatively scored (0–3) across four compartments: membranous, cytoplasmic, nuclear, and inflammatory infiltrate. Statistical analysis included Mann–Whitney U tests with effect size calculations and receiver operating characteristic (ROC) analysis with bootstrap confidence intervals. Results: Psoriasis lesions demonstrated significantly higher total expression scores compared with psoriasiform dermatitis for IL-17A (median 8 vs. 4, p < 0.001, r = 0.847), IL-1β (8 vs. 4, p < 0.001, r = 0.847), TNF-α (8 vs. 4, p < 0.001, r = 0.819), and ICAM-1 (9 vs. 4, p = 0.003, r = 0.637). VCAM-1 showed a higher median expression score in psoriasis (7 vs. 6), but the difference was not statistically significant (p = 0.134, r = 0.322). Structural markers Collagen IV (p = 0.110) and S100B (p = 0.504) showed no significant differences. ROC analysis yielded an AUC of 1.000 for both IL-17A and IL-1β, followed by TNF-α (AUC = 0.983) and ICAM-1 (AUC = 0.876). VCAM-1 exhibited moderate discriminative ability (AUC = 0.694). A combined biomarker panel (IL-17A, TNF-α, and ICAM-1) achieved an AUC of 1.000 within this study cohort; however, this exploratory finding requires external validation. Conclusions: IL-17A, IL-1β, TNF-α, and ICAM-1 represent the most discriminative immunohistochemical markers separating psoriasis from psoriasiform dermatitis. In this preliminary study, IL-17A, IL-1β, TNF-α, and ICAM-1 showed the greatest between-group differences and the highest diagnostic performance within the investigated cohort. VCAM-1 may provide complementary diagnostic information. Collagen IV and S100B appear less useful as standalone discriminators. These findings support the potential role of biomarker-guided precision dermatopathology, although validation in larger independent cohorts is required before clinical implementation.