Recognizing syndromic hidradenitis suppurativa: a review of the literature

Hidradenitis suppurativa (HS) is an inflammatory skin disease causing painful inflammation and suppuration. It may occur in rare syndromes: follicular occlusion, Bazex–Dupré–Christol, Down's, KID, PAPASH, PASS, PASH, and SAPHO syndromes, as well as Dowling‐Degos disease. An overview of syndromic HS may inform the search for aetiological factors in HS. PubMed, Ovid and Web of Science were systematically searched using ‘(hidradenitis OR acne invers*) AND (syndrome OR KID OR PASS OR PAPA OR PASH OR SAPHO OR bazex‐dupre OR ‘dowling degos’ OR triad OR tetrad)’ and Cochrane Library using ‘hidradenitis OR acne invers*’. A total of 82 articles were included in the final review. We summarize 134 cases collected from the 82 included articles. The syndromes are discussed, focusing on etiopathogenesis, clinical presentation and treatment. This study is based on case reports; therefore, conclusions may be subject to the selection bias. These syndromes are rare; however, it is important to recognize them, as treating them may require a different approach. Three subtypes of syndromic hidradenitis are suggested: syndromes with known genetic abnormalities, syndromes characterized by follicular plugging or structural defects, and syndromes with possible autoinflammatory pathogenesis. There was no universally effective treatment for syndromic HS, and treatment was individualized.     

Diet in hidradenitis suppurativa: a review of published and lay literature

Hidradenitis suppurativa (HS) is a chronic, recurring, inflammatory skin disorder resulting in skin abscesses and sinus tracts of the skin folds. Hidradenitis suppurativa remains a disease with limited treatment options. Management of disease activity with dietary modification has been of considerable interest to the HS patient community. Limited evidence exists to support dietary changes for treatment of HS. Strategies such as eliminating dairy products, limiting simple carbohydrate and sugar intake, and avoiding nightshades (Solanaceae) and foods containing brewer's yeast have been reported to be helpful in some patients. Several supplements have also been touted as beneficial. Herein, we review the existing dietary recommendations in both peer-reviewed and lay literature in an attempt to consolidate and evaluate existing information, while stimulating further inquiry into the role of diet in HS. Although dietary modifications are often of considerable interest to HS patients, there is a paucity of data regarding diet as it relates to HS. It is unclear whether diet may prove to be of value in limiting the severity of HS. Further research is needed to determine the potential benefits of these dietary changes.     

Pyoderma gangrenosum associated with hidradenitis suppurativa: a case report and review of the literature

Pyoderma gangrenosum is an inflammatory disease that has been found to be associated with many systemic illnesses. The case presented here is of a man with a 20-year history of hidradenitis suppurativa who developed pyoderma gangrenosum. The pyoderma lesions appeared as a single outbreak which resolved totally after immunosuppressive treatment. This association has been reported only rarely in the literature. Furthermore, in the cases reported, no relationship was apparent between the activity of both diseases. In all cases the clinical course appeared independent, with no apparent overlap in inflammatory activity or response to the drugs administered.     

The bacteriology of hidradenitis suppurativa: a systematic review

Hidradenitis suppurativa (HS) is a chronic inflammatory disabling skin disease consisting of recurrent nodules, sinuses, fistulas and scarring involving the intertriginous regions. HS is often a therapeutic challenge and most treatments are off‐label. A better understanding of aetiology and pathogenesis of HS may facilitate the development of effective treatment. Although the clinical presentation is strongly reminiscent of bacterial infection, the role of bacteria remains controversial. Studies have isolated an array of different bacteria specimens. Consistent findings of Gram‐positive cocci and Gram‐positive rods including Staphylococus aureus, coagulase‐negative staphylococci (CoNS) and Corynebacterium species in deep tissue samples have been demonstrated in HS and may constitute a central target for the immune system. Efficacy of antibiotics, that is rifampicin, clindamycin or tetracycline, supports a microbial role in disease pathogenesis. However, these antibiotics also work as immunomodulators of especially T cells, and the underlying mechanisms may therefore be more complex. We performed a systematic review of previous studies investigating the bacterial flora in hidradenitis suppurativa. We searched PubMed, EMBASE, Royal Danish Library and Cochrane library (search date 11 December 2014). A total of 66 papers were identified and nine papers published between 1988 and 2014 matched our inclusion criteria, yielding bacteriological data of a total of 324 patients with HS (mean age 36.8 years and female/male ratio 215/109). This overview of the bacteriology may aid researchers and physicians exploring the potential role of bacteria in HS. Furthermore, to stimulate a broader debate, we also present different viewpoints on the possible role of bacteria in HS.     

Thyroid autoimmunity in patients with hidradenitis suppurativa: a case–control study

The aetiopathogenesis of hidradenitis suppurativa (HS) is not fully understood; however, increasing evidence suggests that it may be an immune‐mediated disorder. Autoimmune thyroid disease (AITD) has classically been considered as the ‘paradigm’ of autoimmunity, and it has been linked to a variety of skin disorders. To our knowledge, the prevalence of AITD has not been investigated in patients with HS. The aim of the present study was to assess and compare, for the first time, the prevalence of thyroid autoimmunity in 70 patients with HS and in 70 age‐ and sex‐matched controls. In all participants, thyroid autoantibodies and thyroid function tests were analysed. No statistically significant difference was detected between patients with HS and controls, either for the prevalence of thyroid antibodies or for thyroid function parameters. This lack of an association between HS and thyroid autoimmunity suggests that conventional autoimmune mechanisms may not be implicated in the pathogenesis of HS.     

Risk of infection in patients with hidradenitis suppurativa on biologics or other immunomodulators: a systematic review and meta-analysis

Hidradenitis suppurativa (HS) is a painful skin condition that significantly affects patients’ quality of life. Biologic agents, including anti-TNF agents and IL-17 inhibitors, have shown promise as treatment options for HS. However, there is concern about the increased risk of infections associated with these therapies. We conducted a systematic review and meta-analysis following PRISMA and MOOSE guidelines. We searched PubMed and Embase until February 1, 2023. The primary outcome of interest was the incidence of any infectious complications. Secondary outcomes included serious and opportunistic infections in HS patients treated with biologics or other immunomodulators. Twenty-four studies met our inclusion criteria, comprising 1,696 patients. The pooled incidence rate for any infection was 24.2%, primarily consisting of mild respiratory and skin infections. Subgroup analysis based on the mechanism of action (MOA) showed a pooled incidence of 7.77% for anti-IL1, 14.24% for anti-PDE4, and 21.96% for anti-TNF. Notably, patients receiving anti-IL17 had the highest incidence rate of infection at 33.6%, but the relative risk compared to placebo was not significantly elevated (0.99, 95% CI: 0.86–1.14). Serious infections were rare, with pooled incidences of 0.39% for anti-IL17 and 0.03% for anti-TNF. Opportunistic infections were infrequent, with 10 reported cases, including eight oral candidiasis, one cryptosporidiosis, and one Blastocystis hominis infection. The use of biologic therapies in HS patients does not significantly increase the risk of infectious complications. Additionally, the occurrence of serious or opportunistic infections in HS patients treated with biologics appears to be minimal.     

Cardiovascular disease risk factors in patients with hidradenitis suppurativa: a systematic review and meta‐analysis of observational studies

Hidradenitis suppurativa (HS) is a chronic, inflammatory, debilitating skin disease. The aim of the study was to systematically review the literature and critically answer the question: In patients with HS, do cardiovascular risk factors appear at a significantly higher rate compared with controls? The main search was conducted in Medline, Embase and the Cochrane Central Register. Studies eligible for inclusion were of case–control, cross‐sectional and cohort design, and included comparison of any cardiovascular risk factor(s) in patients with HS with those of control groups. An I² value > 50% was considered to show substantial heterogeneity. In this case, DerSimonian and Laird random‐effect models were considered to compute pooled odds ratios (OR). Otherwise, a fixed‐effects model was suitable. Nine studies, with 6174 patients with HS and 24 993 controls, were included. Significant association of HS with obesity [OR 3·45, 95% confidence interval (CI) 2·20–5·38, P < 0·001], central obesity (OR 2·97, 95% CI 1·41–6·25, P = 0·004), active smoking (OR 4·34, 95% CI 2·48–7·60, P < 0·001), history of smoking (OR 6·34, 95% CI 2·41–16·68, P < 0·001), hypertriglyceridemia (OR 1·67, 95% CI 1·14–2·47, P = 0·009), low high‐density lipoprotein (HDL) (OR 2·48, 95% CI 1·49–4·16, P < 0·001), diabetes (OR 2·85, 95% CI 1·34–6·08, P = 0·007) and metabolic syndrome (OR 2·22, 95% CI 1·62–3·06, P < 0·001) was detected. Associations were significant both in population and hospital patients with HS, with hospital HS groups having uniformly higher ORs than the population HS groups. Causality could not be assessed. Heterogeneity was substantial in all analyses. This systematic review indicated that cardiovascular risk factors appear at a significantly higher rate in patients with HS compared with controls. The need for screening of patients with HS for modifiable cardiovascular risks is emphasized.     

Systemic therapy with immunosuppressive agents and retinoids in hidradenitis suppurativa: a systematic review

Hidradenitis suppurativa (HS) is a difficult disease to treat. Although the pathogenesis of this inflammatory skin disease is largely unknown, the important role of the immune system has been demonstrated in both experimental and clinical studies. Clinicians are therefore increasingly prescribing systemic treatments with immunosuppressive agents, but the more traditionally used systemic retinoids, especially isotretinoin, also remain relatively common therapies. In order to provide an overview of all currently available systemic immunosuppressive agents and retinoids for the treatment of HS, a systematic search was performed using the Medline and Embase databases. All published papers concerning systemic retinoids or immunosuppressive treatments for HS in adults were included. The primary endpoints were the percentages of significant responders, moderate responders and nonresponders. Other endpoints were the relapse rate and adverse events. In total 87 papers were included, comprising 518 patients with HS who were treated with systemic retinoids, biological agents or another immunosuppressive agents, including colchicine, ciclosporin, dapsone or methotrexate. The highest response rates were observed with infliximab, adalimumab and acitretin. Overall, the quality of evidence was low and differed between the agents, making direct comparisons difficult. However, based on the amount of evidence, infliximab and adalimumab were the most effective agents. Acitretin was also effective in HS, although the quality of the evidence was low. The therapeutic effect of isotretinoin is questionable. Randomized controlled trials are needed to confirm the effectiveness of acitretin, and to identify the most effective immunosuppressive agents in HS.