Trichoscopy as a Tool to Evaluate Early Dissecting Cellulitis in Patients Affected by Hidradenitis Suppurativa: A Prospective Monocentric Observational Study

Abstract

Background

Dissecting cellulitis (DC) is a rare neutrophilic dermatosis that leads to cicatricial alopecia. Although DC and Hidradenitis suppurativa (HS) have similar characteristics, their association remains poorly understood.

Objectives

In this prospective observational study, we used trichoscopy to identify subclinical signs of DC in male patients aged 18 years or older, presenting with HS. The objective of this study was to use trichoscopy to identify subclinical signs of DC in patients with confirmed diagnosis of HS.

Method

In this prospective, monocentric, observational study, we used trichoscopy to identify subclinical signs of DC in male patients aged 18 years or older, presenting with HS for their initial visit at our HS outpatient clinic from February 1, 2022, to January 31, 2023.

Results

Of the 23 male patients with HS, 8 (35%) had subclinical trichoscopy findings consistent with DC. The most frequent location was the vertex (6/8), and the majority of patients had early/inflammatory trichoscopic signs of DC (5/8). Additionally, patients with trichoscopic findings consistent with DC had a higher Hurley stage and the International Hidradenitis Suppurativa Severity Score System (IHS4). Among the cases with trichoscopic findings compatible with DC, the majority (6/8) were classified as having a “follicular” HS according to the Canoui-Poitrine classification. Patients were treated according to European S1 guidelines on HS.

Conclusions

This is the first study to evaluate subclinical DC findings in HS patients using trichoscopy. Although the trichoscopic findings of DC are heterogeneous, the use of this non-invasive technique, in conjunction with clinical evaluation, can improve diagnostic accuracy and lead to earlier diagnosis. These findings suggest a potential association between HS and DC, indicating the need for further studies to evaluate this relationship.

Introduction

Dissecting cellulitis (DC), also referred to as “perifolliculitis capitis abscedens et suffodiens,” is a neutrophilic dermatosis of unknown aetiology that ultimately results in cicatricial alopecia. DC is a rare condition that predominantly affects young adult males, with over 80% of affected patients being male. It belongs to the “follicular occlusion tetrad,” a group of conditions that includes hidradenitis suppurativa (HS), acne conglobata, and pilonidal cyst. These four entities are thought to share a common pathogenetic mechanism, in which initial follicular deep occlusion ultimately leads to follicular rupture and subsequent infection [1]. HS is an inflammatory disease that primarily affects the apocrine glands, presenting with painful nodules, abscesses, sinus tracts, and fibrosis, typically in large skin folds. In a paper by Federico et al. [2], the authors suggest that DC and HS may represent different manifestations of the same disease, given their numerous characteristics, ranging from epidemiology to clinic presentation and treatment.

Materials and Methods

We conducted a monocentric, prospective, observational study on consecutive male patients aged 18 years or older presenting for their initial visit at our HS outpatient clinic from February 1, 2022, to January 31, 2023. To avoid potential confounding bias due to the significantly higher prevalence of DC in males, female patients were excluded from the study. The demographic characteristics of the study population are reported in Table 1. Biopsy specimens were obtained from 3 patients with histology compatible with a diagnosis of DC; other patients declined biopsy due to their minimal disease involvement. The objective of this study was to use trichoscopy to identify subclinical signs of DC in patients with confirmed diagnosis of HS in order to better understand the strength of this association, which remains poorly understood (Fig. 1). To our knowledge, this is the first study to evaluate subclinical DC findings in HS patients using this diagnostic approach, which has the potential to reveal a higher number of subclinical DC cases in this population.

Table 1.

Main features of the population studied

Patient No.	DC	Trichoscopic findings type	Area	Hurley stage	Body area	IHS4	Canoui-Poitrine	Smoking	BMI	Age	Follicular tetrad	Familiarity
1	Yes	Early/inflammatory, late/fibrotic	Vertex, occipital	2	Armpit, buttock, groin	6	1	Yes	22	22	Acne conglobata	Yes
2	Yes	Early/inflammatory	Occipital	2	Armpit, buttock, groin	6	2	Yes	22	37	Pilonidal cyst	No
3	Yes	Early/inflammatory, late/fibrotic	Frontal, parietal, temporal, vertex, occipital	3	Armpit, groin, pubic area	10	2	Yes	27	50	NA	No
4	Yes	Early/inflammatory, late/fibrotic	Parietal, vertex, occipital	3	Armpit, scrotum	5	2	Yes	26.5	34	Acne conglobata	Yes
5	Yes	Early/inflammatory	Vertex	2	Armpit	2	2	Yes	28.3	18	NA	No
6	Yes	Early/inflammatory	Vertex	3	Armpit, groin	9	2	No	28.5	38	Acne conglobata	No
7	Yes	Early/inflammatory	Occipital	3	Armpit, groin	4	1	Yes	26.2	21	Acne conglobata	Yes
8	Yes	Early/inflammatory	Vertex	2	Armpit	1	2	No	21.1	27	Acne conglobata	No
9	No	NA	NA	3	Armpit, buttock, groin	9	3	Yes	27.9	32	Pilonidal cyst	No
10	No	NA	NA	2	Armpit, buttock	6	3	Yes	26.4	37	NA	No
11	No	NA	NA	2	Armpit, groin	3	1	Yes	28.8	40	NA	Yes
12	No	NA	NA	2	Armpit, buttock, groin	2	3	Yes	20.6	34	Pilonidal cyst	No
13	No	NA	NA	1	Armpit	3	1	Yes	22.5	30	NA	Yes
14	No	NA	NA	1	Armpit	1	1	No	22.1	21	NA	No
15	No	NA	NA	1	Armpit, Buttock	2	3	Yes	20.6	50	Pilonidal cyst	No
16	No	NA	NA	2	Armpit, Buttock	4	3	Yes	27.6	37	NA	No
17	No	NA	NA	3	Armpit, groin	8	1	Yes	25.6	41	NA	Yes
18	No	NA	NA	2	Armpit	1	1	Yes	20.7	43	Acne conglobata	No
19	No	NA	NA	2	Armpit, groin, pubic area	7	2	Yes	22.4	42	Pilonidal cyst	No
20	No	NA	NA	2	Armpit, buttock, groin, pubic area	13	1	Yes	32.7	47	Pilonidal cyst	No
21	No	NA	NA	1	Facial (preauricular and jaw angle)	4	2	Yes	26.4	41	NA	Yes
22	No	NA	NA	1	Armpit, groin	10	1	No	21.4	29	NA	No
23	No	NA	NA	2	Armpit, buttock, groin	3	3	Yes	29.2	33	Acne conglobata	Yes

IHS4, International Hidradenitis Suppurativa Severity Score System; NA, not applicable.

Early/inflammatory findings: broken hair, black dots, “3D” yellow dots, erythema, peri- and interfollicular scales, pustules, hemorrhagic crusts, and large brown dots. Late/fibrotic findings: structureless white areas, white, blue-grey, and red dots, punctate vessels, and polytrichia.

Fig. 1.

Trischoscopic findings in patients affected by HS. a, b Patient number 1 had two small alopecic patches with loss of follicular openings and white structureless areas (red box). c, d Patient number 4 showed 6 hairs emerging from a skin cleft (red arrow) and large yellow dots (yellow arrow). e, f Patient number 7 had large perifollicular pustules surrounded by pinpoint vessels and short regrowing hairs (yellow box).

Although the trichoscopic findings of DC are numerous and heterogeneous and can vary depending on the disease stage, the use of this non-invasive technique, in conjunction with clinical evaluation, can improve diagnostic accuracy and lead to earlier diagnosis [3]. In the early stage of the disease, broken hair and black dots may be observed [4]. Big, double-bordered yellow dots, which have a characteristic “soap bubble” or “3D” appearance, are considered DC’s most specific trichoscopic finding and represent sebum accumulation in the follicular infundibulum [3]. During the inflammatory phase, erythema and peri- and interfollicular scales can be seen as well as pustules and hemorrhagic crusts. In addition, large brown dots, which represent follicular openings, are commonly observed [5]. In the later stages of the disease, fibrosis becomes the dominant feature, and trichoscopic findings may include structureless white areas and white, blue-grey, and red dots as well as punctate vessels and polytrichia (defined as the presence of five or more shafts per follicular unit) [3]. Unfortunately, at this point, there is typically a poor response to therapy.

Results

In our study, we found that 8/23 (35%) male patients with HS had subclinical trichoscopy findings compatible with DC. We did not detect any clinical signs of ectopic or atypical HS phenotype, such as involvement of the facial or nape area, in the scalp of our patients. Furthermore, we did not observe any other pathological condition that could justify the trichoscopic picture detected. The most frequent location was the vertex (6/8), followed by the occiput (5/8). The majority of the patients had early/inflammatory trichoscopic signs of DC (5/8), while only 3 patients had concomitant late/fibrotic findings. Interestingly, the Hurley stage of patients with a trichoscopy consistent with DC was higher than those without DC (2 patients with a Hurley stage 2 and 2 patients with a Hurley stage 3 vs. 5 patients with a Hurley stage 1, 8 patients with a Hurley stage 2 and 2 patients with a Hurley stage 3), as well as the International Hidradenitis Suppurativa Severity Score System (IHS4) (5.3 ± 3.1 vs. 5 ± 3.6); on the other hand, the average BMI in the 2 groups was the same (25.2 ± 3 in the group with the DC vs. 25.2 ± 3.6). Among the cases with trichoscopic findings compatible with DC, the majority (6/8) were classified as having a “follicular” HS according to the Canoui-Poitrine classification, indicating that the prevailing clinical manifestations were follicular lesions, including epidermal cysts, comedones, and pilonidal sinus [6]. Patients were treated according to the European S1 guidelines on HS; 8 patients were administered a 12-week 100 mg/day course of doxycycline (4/8) or lymecycline 300 mg/day for 3 months, 4 received a combination of rifampicin and clindamycin 600 mg + 600 mg/daily for 12 weeks, 4 patients with mild HS were instructed to apply topical clindamycin on inflammatory lesions, 3 patients were screened for anti TNF-α drugs and started adalimumab 40 mg/weekly, 3 patients were treated with oral zinc 90 mg/day for 4 months, 1 patient refused any treatment. The majority of patients (6/8) with positive trichoscopic signs was treated with tetracycline, and the remaining 25% received adalimumab.

Discussion

These results are in line with the hypothesis made by Federico and colleagues, which considers DC and HS as different expressions of the same entity [2], and suggest that the relationship between DC and HS may be closer than previously thought. The higher Hurley stage found in patients with trichoscopic findings suggestive of DC seems to further corroborate this thesis and shows that the stronger the inflammatory load, the higher the risk of developing a DC. Identifying DC in HS patients early on can lead to a more timely diagnosis and treatment, which is important for preventing the long-term consequences of DC. Overall, these results underscore the value of trichoscopy as a non-invasive tool for detecting subclinical signs of DC in HS patients.

Statement of Ethics

All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship for this article, take responsibility for the integrity of the work as a whole, and have given their approval for this version to be published. The study was performed in line with the Declaration of Helsinki (1964) and its subsequent amendments. The subjects were informed about the expected benefits of the tested products and the constraints of study participation and signed an informed consent form, including consent for the use of photographs taken prior to and during the study. Written informed consent was obtained from the patients for publication of the details of their medical case and any accompanying images.

Samples used in this study were obtained as part of routine medical care. Ethical approval for use of these samples for research purposes was not required for this study in accordance with local/national guidelines.

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Funding Sources

No funds were received for the present study.

Author Contributions

Marco May Lee wrote the majority of the paper, Luigi Naldi revised the paper critically, Bianca Maria Piraccini is accountable for the accuracy of the work, Michela Starace and Aurora Alessandrini made a substantial contribution to the study design, and Andrea Sechi acquired the data and gave the final approval for the paper.

Funding Statement

No funds were received for the present study.

Data Availability Statement

All data generated or analysed during this study are included in this article. Further enquiries can be directed to the corresponding author.