The Incidence of Acantholysis in Pityriasis Rubra Pilaris-Histopathological Study Using Multiple-Step Sections and Clinicopathologic Correlations.

Background: The classical histopathological findings in the epidermis of pityriasis rubra pilaris (PRP) do not include acantholysis; however, acantholysis was described in several case reports and a few series of PRP with variable frequencies. We sought to establish the incidence of acantholysis in biopsies from consecutively referred PRP cases using multiple-step sections and clinicopathologic correlations.

Methods: Twenty-three biopsies from 12 consecutively referred patients with classical (type 1) PRP were studied histopathologically. Each specimen was completely step sectioned. The clinical files of the patients were also reviewed.

Results: Small foci of acantholysis were observed in some of the step sections of 5 of 23 (22%) biopsies obtained from 4 patients. Three biopsies showed suprabasal acantholysis, 1 of which also demonstrated mild dyskeratosis and 2 showed midepidermal acantholytic foci as well. The remaining 2 biopsies demonstrated midepidermal and subcorneal acantholysis, respectively. Small erosions were described in the physical examination of 2 of the 4 (50%) patients with acantholysis and in 1 of the 8 (12.5%) patients without acantholysis.

Limitations: The number of cases.

Conclusions: Small foci of acantholysis may be found in the minority of PRP biopsies, and it may be related to small erosions clinically in some patients.