Background: Pseudopelade of Brocq (PB) is a permanent progressive scarring alopecia characterized by numerous alopecic patches localized only in the scalp, that tend to coalesce into larger, irregular plaques with policyclic borders. PB can be considered either the final atrophic stage of several scarring disorders such as lichen planus pilaris (LPP) and discoid lupus erythematosus (DLE) (secondary PB) or an autonomous disease (primary PB). The aim of this study was to assess the incidence of primary vs. secondary PB by a combined histopathological and immunopathological study in a series of patients who fulfilled the clinical diagnostic criteria for PB set forth by Braun Falco et al.
Methods: We studied 33 patients (5 males and 28 females, whose age ranged from 24 to 75 years). The duration of the disease (from onset to biopsy) ranged from 3 months to 8 years. Serum samples were tested for circulating auto-antibodies (antinuclear antibodies anti ENA, anticentromere, anti-Scl70, antithyroid, antigastric parietal cells) circulating immune complexes, total and single fraction (C3, C4) complement activity. The skin biopsies taken from the active advancing margin of the more recent alopecic patch were bisected vertically, one was sent for histopathological examination, and the other for the immunofluorescence studies.
Results: In all patients the serum tests above were found to be negative or normal. Histopathologically, 11 biopsies (33.3%) displayed findings typical for LPP whereas seven cases (21.2%) showed typical DLE features. In the remaining 15 cases (45.5%) histopathological findings were not suggestive of any specific dermatosis. DIF investigations showed findings typical of LPP in six cases (18.1%) and typical of DLE in seven cases (21%). In three cases we did not find findings typical of LPP, DLE, or any other specific dermatitis. In 11 cases no immunological deposits could be detected and therefore were classified as negative.
Conclusion: In conclusion, PB is a type of scarring alopecia of the scalp associated with a peculiar clinical presentation and evolution, which cannot be considered an autonomous nosologic entity because in 66.6% of patients it is the end stage of other inflammatory chronic diseases such as LPP and DLE. It is conceivable that even in those cases in which the histopathological and immunopathological findings did not allow for a specific diagnosis, LPP and DLE were also involved. It is noteworthy that in our study the histopathological and the immunopathological examinations did not conflict and often the results were even coincidental, thus confirming the compatibility of the combined histo-immunopathological approach in the diagnostic evaluation of PB.