Acta Dermato-Venereologica 99-3CompleteContent

351 SHORT COMMUNICATION Prevalence and Description of Hidradenitis Suppurativa in Down Syndrome: A Cross-sectional Study of 783 Subjects Florence POIZEAU 1 , Emilie SBIDIAN 1,2 , Clotilde MIRCHER 3 , Anne-Sophie REBILLAT 3 , Olivier CHOSIDOW 1,2 , Pierre WOLKENSTEIN 1,2 , Aimé RAVEL 3# and Claire HOTZ 1# 1 Department of Dermatology, Henri Mondor Hospital, Assistance Publique Hôpitaux de Paris, 51 avenue du Maréchal de Lattre de Tassigny, FR-94000 Créteil, 2 EA EpiDermE 7379, Paris Est University, Créteil, and 3 Jérôme Lejeune Institut, Paris, France. E-mail: florence.poizeau@ wanadoo.fr # These authors contributed equally to this work. Accepted Nov 20, 2018; E-published Nov 21, 2018 Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease characterized by recurrent painful deep nodules and abscesses of the axillary, breast, groin and anogenital regions (1). The estimated prevalence of HS in the European general population is 0.1–4.1% (2, 3). HS is thought to be more frequent in patients with Down syndrome (DS) (4, 5). However, the prevalence of HS in patients with DS has not been estimated in the clinical setting. The following hypothesis of a genetic link with DS could explain the suggested increased risk of HS in this population. Gamma-secretase, a transmembrane protease, plays a key role in HS (6). Gamma-secretase cleaves the Notch receptor and amyloid precursor protein (APP). Accumulation of APP in DS may occur due to trisomy of chromosome 21 in DS, since the gene encoding APP is located on this chromosome. APP and Notch receptor are competitive substrates for γ-secretase; therefore it is possible that processing of the large amount of APP might occur at the expense of Notch signalling (5). More- over, because another APP cleavage product stimulates keratinocyte proliferation, patients with DS might be susceptible to follicular plugging, which characterizes HS. The aims of this study were to describe HS and to assess the prevalence of the condition in a French po- pulation with DS. METHODS This cross-sectional study of prevalence of HS was performed in a French centre for DS. Physicians were trained in the identification of HS and, for every new DS patient aged 8 years and over, they completed a questionnaire based on the definition of HS. Partici- pants were asked, “Have you ever had large, painful, deep-seated nodules or boils?” If the answer was “yes”, and if the lesions were recurrent and located on compatible areas (groin, armpits, genita- lia, under the breasts, buttocks), the participant was considered to have HS. Epidemiological data were collected and all patients with a diagnosis of HS were referred to the department of dermatology. RESULTS Among the 783 participants with DS included in the study from December 2015 to March 2017, 114 had HS. The estimated prevalence of HS was 14.6% (95% confidence interval 12.3–17.2%). The median age of the DS population was 29 years (range 9–67 years). The sex ratio of HS and non-HS participants was similar (Table I). Obesity (body mass index (BMI) ≥30 kg/m 2 ) and a non-white phototype were more frequent in subjects with HS than in those without HS (Table I). Only 6/783 participants smoked. In total, 17 patients were examined by a dermatologist, and a diagnosis of HS was confirmed in all cases. Eleven of the 17 patients were female, median age was 22 years, and median BMI 26.6 kg/m 2 . None of the 17 patients smoked. None had a family history of HS or an associa- tion with an inflammatory disease. The disease was mild in these patients: 9 patients had Hurley stage I disease, 7 had stage II disease, and 1 had stage III disease. The classical axillary-mammary phenotype was predominant (10 vs. 5 patients with a follicular phenotype, and 2 with a gluteal phenotype) (7). DISCUSSION The estimated prevalence of HS in the study population of 783 participants with DS was 15%. However, mis- classification bias may have occurred, as not all of the patients were checked by a dermatologist. To minimize bias, the physicians in the centre underwent training in the clinical signs of HS before and during the study period. Data on any symptoms found were collected. In addition, age may be a confounding factor, since individuals with DS are younger than the general popula- tion. The age distribution in our centre was representative of the general populations of individuals with DS. In order to make a more reliable comparison among stud- ies and to increase the generalizability of our results, the crude prevalence was age-adjusted using the US DS population as a standard (n = 78,842 DS individuals) (8). Table I. Characteristics of patients with Down syndrome with and without hidradenitis suppurativa (HS) Characteristics HS n = 114 Non-HS n = 669 Sex (female), n (%) 59 (51.8) 304 (45.5) Age, median (range) 23 (10–53) 31 (9–67) BMI ≥30 kg/m 2 , n (%) Non-white phototype, n (%) 35 (33.0) 19 (17.3) BMI, kg/m 2 , median (range) 109 (16.9) 55 (9.2) 0.22 < 10 –4 0.0001 < 10 –4 0.01 BMI: body mass index. This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Journal Compilation © 2019 Acta Dermato-Venereologica. 26.2 (19.7–59.5) 24.6 (15.2–52.3) p-value doi: 10.2340/00015555-3095 Acta Derm Venereol 2019; 99: 351–352

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