Features of Patients With Crohn's Disease and Hidradenitis Suppurativa

Mucocutaneous manifestations of inflammatory bowel disease

Mucocutaneous manifestations can be indicative of a variety of gastrointestinal diseases, and the dermatologist needs to know how to recognize them to refer the right patients to the gastroenterologist. Conversely, the gastroenterologist is often confronted with mucocutaneous lesions that raise the question of a possible association with a known digestive disease. Among the extra-intestinal manifestations of inflammatory bowel disease (IBD), mucocutaneous manifestations are the most common. This review will provide a breakdown by classifying them into 4 groups: 1) reactive manifestations, which include neutrophilic dermatoses, aphthous stomatitis, erythema nodosum, and vasculitis; 2) Crohn's disease-specific granulomatous skin lesions, which are histologically characterized by tuberculoid granulomas similar to those found in the gastrointestinal tract; 3) nutritional deficiency manifestations secondary to anorexia, malabsorption, loss, and drug interactions; and 3) a variety of autonomous autoimmune or inflammatory skin diseases. Dermatologists may also be involved in the management of the adverse effects of IBD treatments, especially the so-called "paradoxical" psoriatic eruptions.

Causal association between inflammatory bowel disease and hidradenitis suppurativa: A two-sample bidirectional Mendelian randomization study

Background

Epidemiological studies have revealed a link between inflammatory bowel disease (IBD) and hidradenitis suppurativa (HS). To determine whether IBD and HS are causally related, we used the Mendelian randomization (MR) approach.

Methods

A two-sample MR was performed using an analysis of 12,882 patients and 21,770 controls with IBD and its main subtypes, ulcerative colitis (UC) and Crohn's disease (CD). A total of 409 cases and 211,139 controls without hidradenitis suppurativa (HS) were included in the data for this condition from various GWAS investigations. Odds ratios (ORs) with 95% confidence intervals (CIs) are used to estimate causal effects.

Results

The study assessed the causal relationship between HS and IBD in both directions. The risk of HS was increased by IBD (IVW OR = 1.34, 95% CI = 1.20-1.49, p = 2.15E-07) and, in addition, HS was affected by UC (IVW OR = 1.27, 95% CI = 1.13-1.43, p = 8.97E-04) and CD (IVW OR = 1.18, 95% CI = 1.08-1.29, p = 4.15E-04). However, there was no evidence of a causal relationship between HS and IBD or its subtypes (IBD IVW OR = 1.00, 95% CI = 0.96-1.05, p = 0.85; UC IVW OR = 0.99, 95% CI = 0.95-1.03, p = 0.65; CD IVW OR = 1.03, 95% CI = 0.98- 1.07, p = 0.28).

Conclusion

This study demonstrates that IBD and its subtypes have a causal effect on HS, whereas HS does not affect IBD. Gut-skin axis interactions may help to understand this association. Nevertheless, further studies are needed to clarify the pathophysiology of the causal relationship between IBD and HS.

Hidradenitis suppurativa and inflammatory bowel disease in a nested case-control study

BACKGROUND

Association between Hidradenitis Suppurativa (HS) and Inflammatory Bowel Disease (IBD) has been suggested.

AIMS

To assess characteristics of HS and IBD in patients with or without concomitant IBD.

METHODS

In a prospective, nested case-control study, each IBD patient with concomitant HS (Case) was retrospectively matched with 4 patients with HS and no IBD (Controls) for gender and age (±5 years).HS was classified according to the Hurley score and the International Hidradenitis Suppurativa Severity Score System (IHS4). Data were expressed as mean (Standard Deviation). Statistical analysis included Student-t Test or Mann-Whitney Test, χ2 test, univariate and multivariate logistic regression.

RESULTS

The study population included 125 patients with HS: 25 with IBD, 100 matched Controls with no IBD. IBD group included 19 (76%) Crohn's disease and 6 (24%) Ulcerative Colitis patients. Obesity, familial HS and perianal HS were less frequent in Cases than in Controls (1[4%] vs 25(25%];p = 0.02; 1[4%] vs 21(21%];p = 0.04; 1[4%] vs 31(31%];p = 0.005, respectively).HS was less severe in Cases when assessed by the IHS4 (5.9 ± 4 vs 9 ± 6.7;p = 0.04).Complete drug-induced response for HS was more frequent in IBD (13[53%] vs28 (28%]; p = 0.04).

CONCLUSION

Clinical characteristics of HS and of patients differed between Cases and Controls. Present findings suggest the need to appropriately search and assess skin lesions compatible with HS in IBD.

Risk Factors for Developing Hidradenitis Suppurativa in Patients With Inflammatory Bowel Disease: A Retrospective Case-Control Study

Background

Hidradenitis suppurativa (HS) is associated with inflammatory bowel disease (IBD), though risk factors remain to be determined.

Aim

To characterize HS among a cohort of IBD patients and identify risk factors for its development.

Methods

This was a retrospective case–control study at the ambulatory IBD centre at Mount Sinai Hospital from inception to May 2019. Patients with IBD who developed HS were included. Cases were matched 5:1 by age, gender (male versus female) and IBD type (ulcerative colitis [UC] or Crohn’s disease [CD]) to controls who had IBD without HS. Conditional logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (95% CIs).

Results

Twenty-nine cases of HS (19 CD and 10 UC) and 145 controls were included. Of the 29 patients with HS, 11 (37.9%) were male and 18 (62.1%) were female. The severity of HS was mild in 10 (34.5%), moderate in 16 (55.2%) and severe in 3 (10.3%) patients. Patients with HS and IBD were more likely to be active (OR 10.3, 95% CI 2.0 to 54.0, P = 0.006) or past (OR 8.4, 95% CI 2.7 to 25.8, P < 0.005) smokers. Patients with HS and IBD were also more likely to have active endoscopic disease (OR 3.8, 95% CI 1.2 to 12.2, P = 0.022). Furthermore, those with HS and CD were more likely to have active perianal disease (OR 21.1, 95% CI 6.2 to 71.9, P < 0.005).

Conclusions

Active IBD, perianal disease and smoking may be associated with HS in IBD. Larger studies are needed to better characterize this morbid condition.

Intra-abdominal and Anorectal Abscesses

Intra-abdominal and anorectal abscesses are common pathologies seen in both inpatient and outpatient settings. To decrease morbidity and mortality, early diagnosis and treatment are essential. After adequate drainage via a percutaneous or incisional approach, patients need to be monitored for worsening symptoms or recurrence and evaluated for the underlying condition that may have contributed to abscess formation.

Association of hidradenitis suppurativa with Crohn’s disease

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disorder characterized by recurrent nodules, abscesses, and sinus tracts. Crohn’s disease (CD) is characterized by inflammation of the entire digestive tract and belongs to the group of inflammatory bowel diseases, and there are many extraintestinal manifestations, among which hidradenitis suppurativa is one of the rare extraintestinal manifestations. There appears to be a strong association between CD and HS based on clinical and histological similarities (sinus tract development, granulomatous inflammation, and scarring), intersections in pathogenesis (genetic loci, immune dysregulation mechanisms, and microbiome changes), and commonality in treatment. In this review, we summarize recent studies on the association between HS and CD.

Increased risk of permanent stoma in Crohn's disease associated with hidradenitis suppurativa: a case-control study

BACKGROUND

Crohn's disease (CD) and hidradenitis suppurativa (HS), a chronic inflammatory skin disease, induce similar inflammatory lesions of the groin and gluteal area. Both diseases are characterised by an inadequate immune response to commensal bacteria in genetically predisposed subjects and can be associated.

AIM

To assess whether HS was associated with clinical and prognostic factors in CD.

METHODS

A retrospective case-control study included 4645 patients with CD referred to Saint-Antoine Hospital gastroenterology tertiary care centre between 2003 and 2016. Matching variables were sex, age, age and the presence of perianal lesions at CD diagnosis, follow-up quality. HS was confirmed by dermatological examination; location, phenotype and severity (Hurley staging) were recorded.

RESULTS

Hidradenitis suppurativa prevalence was 0.95% (44 cases); 80% of patients displayed Hurley stage II or III disease. CD preceded HS in 70% of cases with a median interval of 9 years (IQR 5.25-12.75). CD with HS was more active (56% vs 40% years with active disease, P < 0.001) and required more anti-TNF agents (39% vs 23% years spent with anti-TNF treatment, P < 0.001) than CD without HS. HS was associated with a higher risk of permanent stoma, 16.8% (IQR 7.5-33.3) vs 2.5% (IQR 0.8-7.4) in the control group (P = 0.002). Multivariate analysis confirmed HS as independent risk factor for permanent stoma (odds ratio 6.19; 95% CI, 2.30-38.33; P < 0.001).

CONCLUSIONS

Hidradenitis suppurativa is associated with worse CD prognosis, more active disease and increased risk of permanent stoma, despite a higher use of anti-TNF agents.

Safety of P28GST, a Protein Derived from a Schistosome Helminth Parasite, in Patients with Crohn's Disease: A Pilot Study (ACROHNEM)

Despite the development of novel therapies, inflammatory bowel diseases remain an innovative treatment challenge. Helminth therapy is a new promising approach, and a key issue is the identification of helminth-derived anti-inflammatory mediators. P28 glutathione-S-transferase (P28GST), a protein derived from schistosomes, a trematode parasitic helminth, was shown to reduce intestinal inflammation in experimental colitis by down-regulating the Th1/Th17 response. In this multicenter, open-label, pilot Phase 2a study, we evaluated the safety of P28GST administered to patients with mild Crohn’s disease (CD). We enrolled 10 patients with a baseline Crohn’s disease activity index (CDAI) value <220. Eight patients received two to three subcutaneous injections of recombinant P28GST with adjuvant. This three-month treatment was followed by a nine-month monitoring period. The primary endpoints were the monthly rate and seriousness of adverse events (AEs). Secondary endpoints were clinical recurrence, assessed with the CDAI as well as the levels of immunologic and inflammatory blood and tissue markers. The most common AEs were local or regional events at the injection site and gastrointestinal disorders. At three months after the first injection, CDAI scores and blood calprotectin levels decreased in parallel. These results indicate that P28GST showed promise as a safe and new therapeutic option for treating CD.

Association of Hidradenitis Suppurativa With Inflammatory Bowel Disease: A Systematic Review and Meta-analysis

Importance

Hidradenitis suppurativa (HS) and inflammatory bowel disease (IBD) are inflammatory diseases that share common genetic susceptibility and immunologic features. However, the link between HS and IBD has been largely unclear.

Objective

To conduct a meta-analysis to investigate the association between HS and IBD.

Data Sources

A search of the MEDLINE, Cochrane Central Register of Controlled Trials, and Embase databases yielded 397 relevant studies from inception to June 10, 2018. Two additional studies were supplied by one of the investigators.

Study Selection

Case-control, cross-sectional, or cohort studies that examined the odds or risk of IBD in patients with HS were included. No geographic or language limitations were imposed.

Data Extraction and Synthesis

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. The Newcastle-Ottawa Scale was used to assess the risk of bias of included studies. Crohn disease and ulcerative colitis were analyzed separately, and a random-effects model meta-analysis was conducted.

Main Outcomes and Measures

The odds ratios (ORs) and hazard ratios (HRs) of IBD, Crohn disease, and ulcerative colitis in association with HS.

Results

Five case-control studies, 2 cross-sectional studies, and 1 cohort study with a total of 93 601 unique participants were included. The meta-analysis of case-control and cross-sectional studies showed significant associations of HS with Crohn disease (pooled OR, 2.12; 95% CI, 1.46-3.08) and ulcerative colitis (pooled OR, 1.51; 95% CI, 1.25-1.82). Two case-control studies found significant association of HS with IBD (ORs, 2.16 [95% CI, 1.40-3.34] and 10.00 [95% CI, 1.94-51.50]). One cohort study found an increased risk of IBD in patients with HS (HR, 5.6; 95% CI not reported; P < .002).

Conclusions and Relevance

The evidence to date supports an association of HS with IBD. These results suggest that consultation with gastroenterologists should be sought when patients with HS present with recurrent abdominal pain, chronic diarrhea, bloody stool, and body weight loss.

Diagnosis and treatment of dermatologic diseases in inflammatory bowel disease

PURPOSE OF REVIEW

Dermatologic manifestations in patients with inflammatory bowel disease (IBD) are increasingly recognized as related disorders, secondary to specific therapies used to treat IBD, or complications of IBD itself. These dermatologic manifestations can be difficult to manage.

RECENT FINDINGS

We summarize three categories of dermatologic manifestations in this review: extraintestinal cutaneous disorders, paradoxical manifestations to biologic therapies, and other drug-induced cutaneous manifestations. In particular, we provide current data surrounding clinical characteristics, epidemiology, and treatment modalities for individual cutaneous manifestations.

SUMMARY

Many extraintestinal cutaneous manifestations can be managed by optimized treatment of IBD itself, as shared treatment pathways exist. Paradoxical reactions to biologic agents may be driven by the individual biologic therapy. In these instances, if topical therapies or immunomodulators are not effective in treating the paradoxical cutaneous reaction, a change of class may be required. Nonmelanoma and melanoma skin cancers have been linked to specific therapies for IBD (including thiopurines and antitumor necrosis factor alpha agents, respectively). Therefore, optimizing preventive efforts towards skin cancer is warranted. Recognition of these cutaneous disorders by the practicing gastroenterologist is important, as is collaboration with dermatology for management of many cutaneous disorders.

Hidradenitis suppurativa/acne inversa: a practical framework for treatment optimization - systematic review and recommendations from the HS ALLIANCE working group

Hidradenitis suppurativa (HS)/acne inversa is a debilitating chronic disease that remains poorly understood and difficult to manage. Clinical practice is variable, and there is a need for international, evidence‐based and easily applicable consensus on HS management. We report here the findings of a systematic literature review, which were subsequently used as a basis for the development of international consensus recommendations for the management of patients with HS. A systematic literature review was performed for each of nine clinical questions in HS (defined by an expert steering committee), covering comorbidity assessment, therapy (medical, surgical and combinations) and response to treatment. Included articles underwent data extraction and were graded according to the Oxford Centre for Evidence‐based Medicine criteria. Evidence‐based recommendations were then drafted, refined and voted upon, using a modified Delphi process. Overall, 5310 articles were screened, 171 articles were analysed, and 65 were used to derive recommendations. These articles included six randomized controlled trials plus cohort studies and case series. The highest level of evidence concerned dosing recommendations for topical clindamycin in mild disease (with systemic tetracyclines for more frequent/widespread lesions) and biologic therapy (especially adalimumab) as second‐line agents (following conventional therapy failure). Good‐quality evidence was available for the hidradenitis suppurativa clinical response (HiSCR) as a dichotomous outcome measure in inflammatory areas under treatment. Lower‐level evidence supported recommendations for topical triclosan and oral zinc in mild‐to‐moderate HS, systemic clindamycin and rifampicin in moderate HS and intravenous ertapenem in selected patients with more severe disease. Intralesional or systemic steroids may also be considered. Local surgical excision is suggested for mild‐to‐moderate HS, with wide excision for more extensive disease. Despite a paucity of good‐quality data on management decisions in HS, this systematic review has enabled the development of robust and easily applicable clinical recommendations for international physicians based on graded evidence.

Clinical updates on perianal fistulas in Crohn's disease

Perianal fistulizing disease is an aggressive and debilitating phenotype of Crohn's disease (CD), representing a significant therapeutic challenge. New work has led to advancement in epidemiology and long-term outcomes of perianal disease. The range of therapeutic options continues to expand, including new biologic agents, biosimilars, and stem cell therapy. Areas covered: We discuss updates to all aspects of management of perianal disease, with a focus on the last 3 years of published data. Areas considered include new data on epidemiology and prognostication, medical and surgical therapy, and stem cell therapy. Expert commentary: The presence of perianal disease at CD diagnosis portends a significantly worse disease course. Patients with perianal disease require close monitoring to identify those who are at risk for worsening disease, suboptimal biologic drug levels, and signs of developing neoplasm. With the impending availability of local mesenchymal stem cell therapy, this becomes increasingly important as this therapy, although extremely promising, is thus far only effective in patients without proctitis.

Risk Factors for Hidradenitis Suppurativa in Patients with Inflammatory Bowel Disease

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disorder characterized by recurrent nodules, abscesses, and sinus tracts that can be debilitating and significantly impair quality of life. Small studies and case reports have suggested a possible association between HS and inflammatory bowel disease (IBD).

AIMS

We performed a case-control study to further characterize IBD patients with HS in terms of smoking status, BMI, sites affected by HS, IBD type and features, and IBD medication history.

METHODS

A total of 38 patients with HS and IBD were identified and matched on age, gender, and IBD type to 136 controls with IBD but not HS. Clinical characteristics of interest were obtained through extensive review of the electronic health record.

RESULTS

Among patients with HS and IBD, the most common sites affected by HS were the inguinal, perianal, and axillary regions. Relative to patients with IBD alone, patients with HS and IBD were nearly six times more likely to be current smokers (p < 0.01) and nearly 11 times more likely to be obese (p < 0.01). Patients with HS and Crohn's were significantly more likely to have ileocolonic and perianal disease than patients with CD only (OR 8.31, 95% CI 2.90-23.80 and OR 2.85, 95% CI 1.19-6.81, respectively; p < 0.01 for both).

CONCLUSIONS

Relative to patients with IBD who do not develop HS, patients with IBD and HS are more likely to be overweight or obese, to be former or current smokers, and to have ileocolonic and/or perianal disease.

Hidradenitis Suppurativa Is Characterized by Dysregulation of the Th17:Treg Cell Axis, Which Is Corrected by Anti-TNF Therapy

Hidradenitis suppurativa (HS) is a chronic, inflammatory, and debilitating disease of hair follicles with 1-4% prevalence and high morbidity. There is a dearth of information on the pathogenesis and immune dysregulation underlying HS; therefore, we carried out a detailed analysis of skin-infiltrating T cells. Cells isolated from skin biopsy samples and blood from HS patients and healthy control subjects were analyzed by 16-parameter flow cytometry to provide detailed profiles of CD4 T-cell subsets. We observed substantial infiltration of inflammatory T cells with a striking T helper (Th) type 17-skewed cytokine profile in HS skin; these cells expressed the Th17 lineage marker CD161 and IL-17, as well as proinflammatory cytokines GM-CSF, IL-22, IFN-γ, and tumor necrosis factor. Regulatory T cells were also enriched in HS lesional skin; however, the ratio of Th17 to regulatory T cells was nonetheless highly dysregulated in favor of Th17 cells. In contrast, lesional skin from anti-tumor necrosis factor-treated HS patients who showed substantial clinical improvement exhibited a significant reduction in the frequency of Th17 cells and normalization of the Th17 to regulatory T cell ratio. These data suggest that inhibition of pathogenic IL-17 via tumor necrosis factor blockade is associated with improvement in immune dysregulation in HS and may provide a rationale for targeting IL-17 in the disease.

Hidradenitis suppurativa: from pathogenesis to diagnosis and treatment

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease primarily affecting apocrine gland-rich areas of the body and presenting with painful nodules, abscesses, sinus tracts, and scarring. HS is a multifactorial disease in which genetic and environmental factors play a key role. The primary defect in HS pathophysiology involves follicular occlusion of the folliculopilosebaceous unit, followed by follicular rupture, and immune responses (perifollicular lympho-histiocytic inflammation), finally leading to the development of clinical HS lesions. HS has a destructive impact on the patient’s quality of life, being a very challenging disease. Available treatments are limited, mostly off-label and with high variability in the reported efficacy. Fortunately, a monoclonal antibody against tumor necrosis factor alpha has been recently approved for treatment of moderate to severe HS, offering patients a promising new option. This review focuses on the main features of HS, including epidemiology, clinical aspects, pathogenesis, severity classifications, comorbidities, and currently available treatments.

Inflammatory bowel disease is associated with hidradenitis suppurativa: Results from a multicenter cross-sectional study

BACKGROUND

Hidradenitis suppurativa (HS) is often associated with inflammatory bowel disease (IBD; Crohn's disease or ulcerative colitis). However, the prevalence of IBD in HS patients is unknown.

OBJECTIVE

To determine the prevalence of IBD in HS patients, and determine if patients with HS and IBD have a distinct HS phenotype.

METHODS

For this multicenter, cross-sectional study, HS patients were asked during their first consultation if they had IBD. The diagnosis of IBD was checked in the medical files, and clinical characteristics were collected.

RESULTS

IBD had a prevalence of 3.3% (95% CI 2.3-4.4) in 1076 HS patients. The prevalence of Crohn's disease was 2.5% (95% CI 1.6-3.4) and the prevalence of ulcerative colitis was 0.8% (95% CI 0.3-1.4). HS-IBD patients were less frequently obese (13.9% vs 31.2%, P = .04) than HS-only patients, but there were no differences in gender, family history of HS, disease severity, body areas affected by HS, or smoking status.

LIMITATIONS

The prevalence might be underestimated since HS patients might still develop IBD.

CONCLUSION

The prevalence of IBD in HS patients (3.3%) is 4-8 times higher than the prevalence in the general northern European population (0.41%-0.74%), however HS-IBD patients do not have a distinct HS phenotype.

Hydradenitis suppurativa and inflammatory bowel disease: An unusual, but existing association

Inflammatory bowel disease (IBD) could be associated with several extra-intestinal manifestations (EIMs) involving musculoskeletal, hepatopancreatobiliary, ocular, renal, and pulmonary systems, as well as the skin. In the last years, hidradenitis suppurativa (HS) is acquiring an increasing interest. IBD, especially Crohn’s disease (CD), is among the most reported associated diseases in HS patients. The aim of this paper is to give a brief overview of data showing a possible epidemiologic and pathogenetic association between IBD and HS. We performed a pooled-data analysis of four studies and pooled prevalence of HS in IBD patients was 12.8%, with a 95%CI of 11.7%-13.9%. HS was present in 17.3% of subjects with CD (95%CI: 15.5%-19.1%) and in 8.5% of UC patients (95%CI: 7.0%-9.9%). Some items, especially altered immune imbalance, are generally involved in IBD pathogenesis as well as invoked by HS. Smoking is one of the most relevant risk factors for both disorders, representing a predictor of their severity, despite, actually, there being a lack of studies analyzing a possible shared pathway. A role for inheritance in HS and CD pathogenesis has been supposed. Despite a genetic susceptibility having been demonstrated for both diseases, further studies are needed to investigate a genetic mutual route. Although the pathogenesis of IBD and HS is generally linked to alterations of the immune response, recent findings suggest a role for intestinal and skin microbiota, respectively. In detail, the frequent finding of Staphylococcus aureus and coagulase-negative staphylococci on HS cutaneous lesions suggests a bacterial involvement in disease pathogenesis. Moreover, microflora varies in the different cutaneous regions of the body and, consequently, two different profiles of HS patients have been identified on these bases. On the other hand, it is well-known that intestinal microbiota may be considered as “the explosive mixture” at the origin of IBD despite the exact relationship having not been completely clarified yet. A better comprehension of the role that some bacterial species play in the IBD pathogenesis may be essential to develop appropriate management strategies in the near future. A final point is represented by some similarities in the therapeutic management of HS and IBD, since they may be controlled by immunomodulatory drugs. In conclusion, an unregulated inflammation may cause the lesions typical of both HS and IBD, particularly when they coexist. However, this is still a largely unexplored field.

Two Cases of Paradoxical Hidradenitis Suppurativa while on Adalimumab

Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease characterized by recurring abscesses, nodules, and fistulas predominantly in the groin and axillae. The association between HS and Crohn's disease (CD) has been well documented. Tumor necrosis factor (TNF) inhibitors have shown to be effective in treating both HS and CD. We report 2 patients who developed HS while on TNF inhibitor treatment for CD.

Results of the Fifth Scientific Workshop of the ECCO (II): Pathophysiology of Perianal Fistulizing Disease

The fifth scientific workshop of the European Crohn's and Colitis Organization (ECCO) focused on the relevance of fistulas to the disease course of patients with Crohn's disease (CD). The objectives were to reach a better understanding of the pathophysiological mechanisms underlying the formation of CD fistulas; to identify future topics in fistula research that could provide insights into pathogenesis; to develop novel therapeutic approaches; and to review current therapeutic strategies (with clarification of existing approaches to prevention, diagnosis and treatment). The results of the workshop are presented in two separate manuscripts. This manuscript describes current state-of-the-art knowledge about fistula pathogenesis, including the roles of epithelial-to-mesenchymal transition and cytokine matrix remodelling enzymes, and highlights the common association between fistulas and stenosis in CD. The review also considers the possible roles that genetic predisposition and intestinal microbiota play in fistula development. Finally, it proposes future directions and needs for fistula research that might substantially increase our understanding of this complex condition and help unravel novel therapeutic strategies and specific targets for treatment. Overall, it aims to highlight unanswered questions in fistula research and to provide a framework for future research work.

Hidradenitis suppurativa (HS): An unrecognized paradoxical effect of biologic agents (BA) used in chronic inflammatory diseases

BACKGROUND

Paradoxical hidradenitis suppurativa (HS) induced by biologic agents (BA) is scarcely reported.

OBJECTIVE

We sought to describe the clinical characteristics and outcome of patients developing paradoxical HS under BA.

METHODS

This was a multicenter nationwide retrospective study asking physicians to report all cases of HS, confirmed by a dermatologist, occurring during treatment of an inflammatory disease by a BA.

RESULTS

We included 25 patients (15 inflammatory rheumatism, 9 Crohn's disease, 1 psoriasis) treated by 5 BA (adalimumab = 12, infliximab = 6, etanercept = 4, rituximab = 2, tocilizumab = 1). Median duration of BA exposure before HS onset was 12 (range 1-120) months. Patients were mostly Hurley stage I (n = 13) or II (n = 11). Simultaneously to HS or within 1 year, 11 patients developed additional inflammatory diseases, including paradoxical reactions (psoriasis = 9, Crohn's disease = 3, alopecia areata = 1, erythema elevatum diutinum = 1). Complete improvement of HS was more frequently obtained after BA discontinuation or switch (n = 6/10, 60%) rather than maintenance (n = 1/14, 7%). Reintroducing the same BA resulted in HS relapse in 3 of 3 patients.

LIMITATIONS

Retrospective nature and lack of complete follow-up for some patients are limitations.

CONCLUSION

HS is a rare paradoxical adverse effect of BA, but fortuitous association cannot be excluded in some cases. We observed a trend toward better outcome when the BA was discontinued or switched.