Morphology of Pilonidal Sinus Disease: Some Evidence of Its Being a Unilocalized Type of Hidradenitis Suppurativa

Abstract

Background: The term ‘pilonidal sinus’ (PS) reflects an acute exacerbating, purulent, fistulating chronic inflammation located in the coccyx region. Systematic histological investigations are scarce, and the etiology has remained controversial. Methods: Histological and immunohistochemical characterization of totally excised material of 27 patients (68 specimens) with PS (no antecedent and no current clinical signs of hidradenitis suppurativa, HS) and its correlation with data on HS which we published earlier. Results: Follicular hyperplasia/hyperkeratosis and interfollicular epidermal hyperplasia are main features of PS. Early pathology seems to take place at terminal hair follicles, whereas sinus tract formations are a secondary event. Focused regions show an inflammatory mixed infiltrate consisting of CD3+, CD4+, CD8+, CD68+ and CD79+ cells. Conclusions: PS and HS have various common characteristics at the histological and immunohistochemical level. Considering PS as a unilocalized type of HS, risk factors known in the latter should henceforth be evaluated in PS as well.

Sonographic Comparison of Morphologic Characteristics Between Pilonidal Cysts and Hidradenitis Suppurativa

“…The described characteristics match reported clinical findings on the sex distribution, such as pilonidal cysts being more common in male patients and hidradenitis suppurativa more frequent in female patients, as well as the sonographic appearances of the main anatomic alterations reported in both entities . These findings also reinforce a previous histologic hypothesis that pilonidal cysts might be a localized form of hidradenitis suppurativa . The only acceptable agreement found between the clinical (Hurley) and sonographic staging was not surprising and similar to a previous report because of the underestimation of severity by the Hurley clinical scoring …”

“…Thus, in that study, it was proposed that a pilonidal cyst could be a unilocalized type of hidradenitis suppurativa . Common histologic characteristics between pilonidal cysts and hidradenitis suppurativa in that study included the presence of follicular hyperplasia, hyperkeratosis, and interfollicular epidermal hyperplasia with involvement of the terminal hair follicles and inflammatory mixed infiltrates . Nevertheless, histologic examinations in hidradenitis suppurativa may be limited because of its usual large extent and multizone type of involvement.…”

“…A closer link between pilonidal cysts and hidradenitis suppurativa has been suggested by a histological study of pilonidal cysts from 27 patients that showed similar features as those reported in hidradenitis suppurativa. Thus, in that study, it was proposed that a pilonidal cyst could be a unilocalized type of hidradenitis suppurativa . Common histologic characteristics between pilonidal cysts and hidradenitis suppurativa in that study included the presence of follicular hyperplasia, hyperkeratosis, and interfollicular epidermal hyperplasia with involvement of the terminal hair follicles and inflammatory mixed infiltrates .…”

“…Since both pilonidal cysts and hidradenitis suppurativa present with alterations of the hair, knowledge of the normal sonographic morphologic characteristics of the hair follicles and tracts, which already have been reported in the literature, might be relevant for a better understanding of the alterations in the diseases that constitute the follicular occlusion tetrad, such as pilonidal cysts and hidradenitis suppurativa …”

Novel Approaches in Pilonidal Sinus Treatment

“…In the literature, a wide range of factors is defined in its etiology. Keratin plugs, foreign substance reaction related to hairs and occurrence of dermopathy and debris in the hair follicles in the natal cleft are the factors most frequently held responsible (Page, 1969;von Laffert et al, 2011;Meinero et al, 2014). Pilonidal sinus disease and its treatment cause discomfort, limitation of mobility and deterioration of the quality of life of the patient (Marsh, 2008;Stewart et al, 2008).…”