Are quantitative histopathologic criteria capable of differentiating psoriasis from chronic dermatitis?

Background: There are overlapping features in histopathologic characteristics of psoriasis and chronic dermatitis, which sometimes make the correct diagnosis difficult.

Objective: The aim of this study was to compare the histopathologic diagnostic features of psoriasis with chronic dermatitis quantitatively.

Patients and methods: In this study, 30 patients with psoriasis and 30 patients with chronic dermatitis were included. Diagnosis of psoriasis or chronic dermatitis was based on clinicopathologic correlation. Photos of histopathologic slides were provided by LABOMED Digital Camera and LABOMED Microscope. Width and length of rete ridges, minimal thickness of suprapapillary plates, thickness of epidermis, thickness of hyperkeratotic layer, and minimal thickness of granular layer were determined using Pixel Pro software on micrometer scale.

Results: Suprapapillary plates and granular layer were significantly thicker in patients with chronic dermatitis compared with patients with psoriasis. The rete ridges were longer and wider, the epidermis was thicker, and the parakeratotic layer was also thicker in patients with psoriasis compared with patients with chronic dermatitis, and the difference between these corresponding parameters in the two groups was statistically significant except for thickness of parakeratotic layer. Moreover, the mean ratio of minimal suprapapillary plate's thickness to epidermal thickness and the mean ratio of minimal granular layer's thickness to parakeratotic layer's thickness were significantly higher in patients with chronic dermatitis compared with those with psoriasis.

Conclusion: Despite overlapping histopathologic features in psoriasis and chronic dermatitis, quantitative histopathologic criteria might be valuable for differentiation of these two conditions. Ratios of minimal suprapapillary plate's thickness to epidermal thickness and minimal granular layer's thickness to parakeratotic layer's thickness can be particularly helpful in this regard.