Real-Time Confocal Imaging for Hidradenitis Suppurativa: Description of Morphological Aspects and Focus on the Role of Follicular Ostia

Abstract

<b><i>Background:</i></b> Hidradenitis suppurativa (HS) is a chronic, recurrent, inflammatory skin disease involving the follicular unit. Growing evidence suggests a crucial role of hyperkeratosis, infundibular plugging and perifolliculitis in its pathogenesis. <b><i>Objectives:</i></b> To characterize the microscopic morphology of open comedos using in vivo reflectance confocal microscopy (RCM) and define alterations occurring in HS normal-appearing perilesional skin compared to healthy skin of a control group, discussing therefore microscopic differences. <b><i>Materials and Methods:</i></b> Twenty patients (11 males, 9 females; aged 19–51 years) affected by HS were recruited. RCM was performed on open comedos of axillary/inguinal regions and on normal-appearing skin areas distant at least 1.5 cm from HS lesions. Ten healthy individuals (6 males, 4 females) were included as control group. <b><i>Results:</i></b> RCM aspects of 78 open comedos were explored, observing circular/ovoidal structures disclosing a hyperrefractive amorphous material (72/78, 92.3%) within the infundibular cavity surrounded with a bright (51/78, 65.4%) and regular (52/78, 66.2%) border. Follicular ostia of HS perilesional skin (<i>n</i> = 541) compared to follicular ostia of a control group (<i>n</i> = 321) were characterized by a larger infundibular diameter (183.4 vs. 85.8 µm) and diverged in terms of material collected inside infundibula (44.5 vs. 21%) and keratinization of the border (47.6 vs. 25.5%). <b><i>Conclusion:</i></b> In vivo characterization of open comedos and the recognition of microscopic subclinical alterations of HS normal-appearing skin, compared to healthy skin, could add further insights into the definition of biological events leading to HS manifestations, including the dysregulated process of keratinization.

Hidradenitis suppurativa: Morphologic and vascular study of nodular inflammatory lesions by means of optical coherence tomography

“…This data is in accordance with previous studies which demonstrated that HS lesions are characterized by widening of pilosebaceous units, the presence of a dermal fluid collection and the observation of a high power‐Doppler ultrasound signal in the proximity of the lesions, which decrease after specific therapy, consistently with the resolution of the inflammatory processes 29–33 . In addition, the presence of widened and hyper‐keratinized pilosebaceous units may reflect one of the leading events implicated in HS pathogenesis, which starts with an abnormal infundibular keratizination that causes occlusion and rupture of the follicular ostia 30,34,35 . Afterwards, HS inflammatory process is known to affect the microcirculation network initiating a remodelling process that ends in a vicious cycle of enhanced inflammation and scarring 10,36 …”

Confocal microscopy and optical coherence tomography of inflammatory skin diseases in hairs and pilosebaceous units: A systematic review

“…Two studies described HS in patients using RCM 41 and OCT 35 . Open comedos appeared as round or ovoidal structures, surrounded by a bright borders, assuming a concentric onion‐like hyperkeratinized appearance of lesions 41 . Double and triple comedos characteristic for HS were also identified, Figure 2.…”

“…34,42 RCM can characterize microscopic morphology of open comedos in vivo and define alterations occurring in HS normal-appearing perilesional skin compared to healthy skin. 41 However, the limited depth of RCM resolution does not allow further investigation in later stages of the disease and correlations with other imaging modalities. 41 Furthermore, in all studies including studies conducted on HS 41 and folliculitis decalvans 43 it was impossible to characterize the cytomorphological features of the inflammatory infiltrates due to limited RCM in vivo resolution.…”

“…The 39 studies included concerned the following 10 skin diseases: 14 studies of acne vulgaris, [7][8][9][10][11][12][13][14][15][16][17][18][19][20] nine studies of rosacea, [21][22][23][24][25][26][27][28] four studies of alopecia areata, [30][31][32][33] two studies of HS, 35,41 two studies of folliculitis, 34,42 two studies of folliculitis decalvans, 43,44 two studies of lichen planopilaris, 33,45 two studies of discoid lupus erythemasus, 33,46 one study of frontal fibrosing alopecia 47 and one including one patient with keratosis pilaris. 48 In total, 33 RCM studies, 12 OCT studies and 45 combined.…”

“…Hair follicles in HS perilesional normal-appearing skin, contained round/ovoidal grey structures, sometimes centred by a hair shaft 41 and peri-and interfollicular inflammatory infiltrates containing amorphous material were found at the superficial dermis. 41 OCT showed HS nodules containing one or more hyperkeratinized infundibula at the top and a hypoechogenic area in the dermis. 35 Amorphous material inside the infundibula and an organized inflammatory infiltrate were observed.…”