Pretibial Pruritic Papular Dermatitis: A Comprehensive Clinical and Pathologic Review of Cases at a Single Institution

Abstract

Background: Studies characterizing clinical and pathologic details of pretibial pruritic papular dermatitis (PPPD) are scarce. Several cases of PPPD at our institution have displayed lymphocyte atypia and CD30 positivity, resembling lymphomatoid papulosis (LyP). We explore the clinical and histological spectrum of PPPD, with emphasis on lymphocyte atypia. Methods: Retrospective observational study of 40 archived pathological specimens (hematoxylin/eosin, CD3, CD20, and CD30 immunohistochemistry) from 38 PPPD patients in an academic center. Clinical photographs were available in 22 cases. Results: Microscopic epidermal changes were focal, but common (spongiosis 75%, parakeratosis 90%, interface changes 43%, Langerhans cell microgranulomas 25%, multinucleated keratinocytes 55%, Civatte bodies 55%, erosion 20%, and more than focal irregular psoriasiform hyperplasia 37%) and certain dermal changes were universal (papillary dermal fibrosis 100%, stellate fibroblasts 100%, and multinucleated fibroblasts 93%). At least focal lymphocyte atypia was present in all cases. Lymphocytes were almost exclusively CD3+ T cells with rare CD20+ B cells. Up to 30% of lymphocytes exhibited weak CD30 staining. Clinically, all cases exhibited discrete papules, but plaques and erosions were not uncommon. Limitations: As a retrospective series, clinical images were not available for all cases. Conclusion: This study suggests a broader histological and clinical spectrum of PPPD than previously described. Epidermal changes are common in PPPD, as are atypical lymphocytes and focal CD30 positivity. Although the papular clinical appearance, lymphocyte atypia, and focal CD30 positivity may resemble LyP, the relatively low number of atypical lymphocytes, low intensity of CD30 staining, and absence of spontaneous resolution help to distinguish PPPD from LyP.

A case report and differential diagnosis of pruritic pretibial skin lesions

“…The latest comprehensive clinical and pathologic review focuses on lymphocyte atypia and CD30 expression in tissue biopsy to distinguish PPPD from lymphomatoid papulosis. The authors concluded that a relatively low number of atypical lymphocytes with weak or light CD30 staining intensity, as well as characteristic pruritus and pretibial distribution, favor PPPD over lymphomatoid papulosis (15).…”

Pretibial Pruritic Papular Dermatitis: A Case Report and Emphasis on Effective Treatment with Pentoxifylline

“… 1 , 2 , 4 , 5 However, in 2019, Flores et al broadened the clinical and histological spectrum of PPPD in 38 patients, demonstrating its epidermal changes. 6 Lesions typically limit to unilateral or bilateral shins. Its prevalence is considered underestimated since the lack of disease recognition and misdiagnosis may occur.…”

“…Histological hallmarks of PPPD are the presence of superficial perivascular and interstitial lymphohistiocytic infiltration, epidermal changes of spongiosis and parakeratosis, and numerous stellate and multinucleated fibroblasts in the dermis. 1 , 2 , 6 The histological features that indicate persistent rubbing, consisting of uneven psoriasiform epidermal hyperplasia, marked compact orthokeratosis, hypergranulosis, and coarse bundles of collagen arranged in vertical streaks, are absent in PPPD, 1 , 2 , 6 and the lack of amyloid deposits in the dermis distinguishes PPPD from LA. 1 , 13 Despite unique PPPD histopathology, its pathogenesis has yet to be fully understood.…”

Pruritic papules of the leg

“…It is thought to arise from chronic rubbing. PPPD was first reported in 2006, [3][4][5] and is likely an under-reported condition. As such, epidemiological data are limited.…”

“…As such, epidemiological data are limited. Based on the two case series that are available (n=44+38=82), 3,4 the median age of onset is 50-60 years, with female dominance (1:3).…”