Clinical Characteristics of a Canadian Cohort of Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a chronic inflammatory skin condition characterized by painful nodules, abscesses and sinus tracts affecting apocrine-bearing skin. Despite its debilitating impact, HS remains poorly understood and frequently misdiagnosed, resulting in diagnostic delays averaging 10 years [1]. Misdiagnosis is particularly pronounced in diverse populations, where racial and ethnic factors may influence disease presentation and outcomes. This knowledge gap impedes the ability of physicians to effectively categorize and treat patients with personalized management plans [2]. Few observational studies on the demographic and clinical characteristics of HS exist in Canada, and arguably none exist in ethnically and racially diverse centres such as Toronto. We conducted a single-site cross-sectional study at Women's College Hospital (Toronto, Canada) from 2022 to 2024. Our cohort consisted of 113 patients diagnosed with HS, and data were collected through structured surveys and medical records. Sociodemographic details, clinical characteristics and disease staging using the Hurley staging system were analysed using SPSS version 28.0. Our findings align with international literature [3, 4] regarding the predominance of HS in female patients (F:M ratio ~3:1) and its association with obesity (BMI, mean ± SD, 31.7 ± 7.8) (Table 1). We confirmed a significant diagnostic delay (9.9 years), consistent with previous reports [3, 4] (Table 1). Furthermore, our study revealed a correlation between disease severity and impaired quality of life (DLQI score 7.6 vs. 12.2 vs. 12.3, p < 0.02) (Table 2). Notably, we observed variations in affected body areas by sex, with a higher prevalence of HS in the groin among females (f 72.6%/m 41.4%, p < 0.005), and a greater incidence on the arms and legs, head and back and shoulders in males (f 2.4%/m 13.8%, p = 0.04) (Table 1). Although not reaching statistical significance, there was a trend suggesting sex-based differences in chest and under-breast involvement. Specifically, under-breast involvement appeared more common in females, and chest involvement in males, which aligns with findings from other studies, warranting further investigation given our small sample size (Table 1). Analysis of past treatments showed that oral antibiotics were the most commonly used (77%), with doxycycline or minocycline being the preferred choices (65.5%). Additionally, topical medications (67.3%) and antiseptic washes (40.7%) were frequently used. Notably, biologics were more commonly administered to males (f 14.3%/m 37.9%, p = 0.01), likely reflecting the higher prevalence of severe HS in males within our cohort (Table 1) [7, 8]. Despite the reported higher prevalence of HS in Black populations by a study conducted in the United States of America [5], our study found a higher proportion of White patients affected by HS compared to Black patients (w 39.8%/b 17.7%). However, when contextualizing these findings with Toronto's racial demographics—43.5% White and 9.6% Black [6]—we noted a disproportionate impact of HS on the Black community relative to their representation in the general population. Additionally, there was a trend indicating greater disease severity among Black patients compared to white patients, Asian patients or other races (b 45%/w 13.4%/a 15.4%/o 9.1%, p = 0.04) according to Hurley stage analysis, highlighting potential disparities in disease progression and outcomes across racial groups. Affected body site patterns also varied by race. Patients categorized as ‘other’ more frequently presented with chest lesions compared to White, Asian, or Black patients (o 13.6%/w 0%/a 3.8%/b 0%; p = 0.04). While not statistically significant, there was a trend towards more lesions on the arms and legs in Asian patients (a 19.2%/w6.7%/b10.7/o 4.5%; p = 0.09). Additionally, White patients more commonly received Cephalexin (w 22.2%, p = 0.01). While HS predominantly affects females (f 74.3%/m 25.7%), further analysis revealed that mild to moderate HS was more common in females (f 57.1%/m 17.2%), whereas severe HS was more prevalent among males (f 9.5%/m 44.8%). This is notable given Toronto's general sex distribution (52% female vs. 48% male) [6], and the greater proportion of males with severe HS were Asian. Our study provided novel insights into referral patterns to our HS clinic, showing that patients were predominantly referred by family physicians or dermatologists (fp 57.7%/d 17.7%). Interestingly, more females were referred by family doctors (f 64.3%/m 37.9%), while more males were referred by dermatologists (f 15.5%/m 24.1%). Moreover, a near significant difference was observed in the provider making the initial HS diagnosis across racial groups. This may suggest differences in access to specialists or referral pathways, with potential clinical implications for timely and accurate diagnosis. In summary, while our study represents the first comprehensive characterization of HS in a multicultural Canadian population, its findings are limited by potential recall bias in self-reported data, selection bias from being a single-centre study, and small sample size (n = 113). The small sample size limits the study's power, particularly for subgroup analyses. Consequently, caution is needed when generalizing these results to all of Canada or North America, and larger, multi-centre studies with diverse cohorts are necessary to confirm these findings. Our research emphasizes the need for continued epidemiological investigations into HS across diverse populations. Geographic, genetic and ethnic factors likely influence disease manifestation and outcomes, highlighting the necessity for tailored diagnostic and therapeutic approaches. Enhancing our understanding of HS epidemiology through future research can lead to optimized care and better outcomes for individuals affected by this challenging condition. Lily Acheampong: conceptualization, methodology, data collection, formal analysis, writing. David Croitoru: methodology, data collection, formal analysis, investigation, writing–review and editing. Marissa Joseph: conceptualization, methodology, data collection, writing–review and editing. Raed Alhusayen: methodology, writing–review and editing. Nesrine Brahimi: methodology, data collection, review and editing. Vincent Piguet: conceptualization, methodology, data collection, supervision, funding acquisition, writing. We also acknowledge Dr William Midodzi (PHD) for contributing to data analysis. This study was funded by AFP Innovation. Ethical approval was reviewed and approved by Women's College Hospital Ethics Committee (REB # 2021-0134-B). All patients in this manuscript have given written informed consent for participation in the study and the use of their deidentified, anonymized, aggregated data and their case details for publication. Dr. Vincent Piguet has received grants from AbbVie, Bausch Health, Celgene, Eli Lilly, Incyte, Janssen, LEO Pharma, L'Oréal, Novartis, Organon, Pfizer, Sandoz, Sanofi and Bristol Myers Squibb; received payment or honoraria for speaking engagement from Sanofi; participated on an advisory board for LEO Pharma, Novartis, Sanofi and Union Therapeutics; and received equipment donation from L'Oréal. Dr. David Croitoru has received consultation fees and educational grants from AbbVie, Amgen, Arcutis, Bausche, BioJAMP, Boehringer-Ingelheim, Bristol-Myers-Squibb, Eli-Lilly, Janssen, Novartis, Pfizer, Sanofi-Regeneron, Sun Pharma, UCB. Dr. Raed Alhusayen has received honoraria for consulting and/or speaking for AbbVie, Fresenius Kabi, Incyte, Janssen, Novartis, Pfizer, UCB and received research funding from AbbVie, Incyte, Jansen. The other authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.

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