Comorbidity screening in hidradenitis suppurativa: Evidence-based recommendations from the US and Canadian Hidradenitis Suppurativa Foundations

1As a chronic suppurating inflammatory disease, hidradenitis suppurativa (HS) exemplifies the potential link between integumentary and systemic disease. Indeed, HS is associated with higher overall comorbidity burden than exists for either healthy or psoriasis populations. This burden also influences mortality risk. The disproportionate prevalence of HS in women and Black patients intensifies the need to identify comorbidities and mitigate their impact. Herein, the US and Canadian HS Foundations have provided evidence-based screening recommendations to support early recognition and treatment of comorbid conditions with the goal of improving long-term health outcomes for patients with HS.

2The scope, content, synthesis of evidence, method of rating quality of evidence, and provisos are described in the Supplemental Materials (available via Mendeley at https://doi.org/10.17632/j52xjybbhg.1).

3Some screenings may be out of scope for dermatologists. We recommend that dermatologists perform examinations for comorbid conditions involving the skin and a simple review of systems for extracutaneous comorbidities. Individual screenings may be prioritized and distributed across visits as is feasible. Dermatologists may serve as advocates by directing primary physicians to potential comorbidities for which screening is recommended.

4The level of evidence and screening recommendations, including suggested methods and roles for the dermatologist, are summarized in Tables I and II.–

5Like HS, acne is a disease of the pilosebaceous unit that affects young adults, has female predominance, and may be mediated by androgens. Acne and HS may also share common inflammatory pathways involving the follicular unit.

6Higher prevalence of acne vulgaris/conglobata among patients with HS compared to control individuals was observed across 4 studies, with the prevalences ranging from 4.5% to 15.2%.– The odds of having acne vulgaris/conglobata were 1.77 to 5.07 times greater in patients with HS.– There were no large-scale studies addressing the prevalence of acne fulminans in patients with HS.

7Dissecting cellulitis of the scalp (DCS) and HS are suppurative conditions involving the follicular unit characterized by perifollicular inflammatory nodules and interconnected draining tunnels eventuating in scarring. Some consider DCS to represent HS of the scalp.

8In one study of more than 5000 patients with HS, DCS prevalence was 9.2%, compared to 0.7% in matched control individuals. The risk of DCS in patients with HS was 13.38 (95% confidence interval [CI], 9.60–18.64) times greater.

9Pilonidal disease (PD) and HS are chronic inflammatory diseases of follicular occlusion characterized by perifollicular inflammatory nodules and draining tunnels.

10Across 2 large-scale studies and 1 small retrospective cohort study, PD prevalences among patients with HS ranged from 1.4% to 2.3%, compared with 0.1% to 0.3% in control individuals.– The prevalence of PD may be greater among patients with severe HS. Adjusted odds of PD among patients with HS ranged from 4.97 to 5.61 times that of control individuals.–

11HS and pyoderma gangrenosum (PG) share clinical features, including similar demographic composition, presence of suppurating plaques and ulcers, neutrophil rich inflammation, response to tumor necrosis factor (TNF) inhibitors, and coexistence as part of autoinflammatory syndromes.

12The prevalence of PG among patients with HS ranges from 0.2% to 0.4%., Prevalence is higher (3.7%) among patients with HS having Crohn’s disease (CD). In a study of 65,000 patients with HS, the adjusted odds of having PG was up to 20 times greater among patients with HS (0.18%) compared to control individuals (0.01%). The association was independent of CD status.

13Local and systemic inflammation and exposures to immunomodulating therapies may increase reactivation risk. Introduction of a highly effective herpes zoster (HZ) vaccine has also increased the relevance of identifying individuals at elevated risk.

14In a retrospective study, hospitalized patients with HS had 1.65 (95% CI, 1.13–2.39) times the odds of HZ compared to hospitalized control individuals, although absolute prevalence was low in both groups (0.143% vs 0.145%). In another retrospective cohort study of 30,000 patients with HS, those not receiving immunosuppression had an incidence of 0.4%. Patients with exposure to immunosuppression had a crude HZ incidence of 1.3%, although this burden still approximated that observed in the general US population (1.0%). The adjusted odds ratio (aOR) of developing HZ among patients with HS was similar regardless of immunosuppression status, suggesting that immunosuppression does not modify the relationship between HS and HZ.

15The pathogenesis of HS and major depression may be linked through increased expression of proinflammatory cytokines, including interleukin (IL) 6 and TNF, which are observed at higher levels in both conditions. Additionally, HS has substantial impact on health-related quality of life, which likely contributes to risk of depression, anxiety, and suicidality.

16The prevalence of depression in HS populations is as high as 26%. The adjusted odds of depression among patients with HS ranges from 1.3 to 4.8 times that of control populations.,– The prevalence of depression may be greater among patients with a higher Hurley stage.

17In a meta-analysis, the prevalence of generalized anxiety disorder among patients with HS was approximately 5%. In a prospective community-based study, patients with HS had 1.7 times the odds of anxiety compared to control individuals. Larger retrospective clinical and administrative database studies have also described higher prevalences and likelihoods of anxiety among patients with HS compared to control individuals.,

18Evidence from European national registries indicates higher incidence of completed suicide among patients with HS. In a Finnish study, 4.4% of deaths in patients with HS were caused by suicide compared to 1.8% of deaths in control individuals, and risk of suicide was 2.8 (95% CI, 1.7–4.5) times higher in patients with HS. In Denmark, patients with HS were observed to have a crude incidence of completed suicide of 0.3 per 1000 person-years, with an increased adjusted risk of 2.4 (95% CI, 1.1–5.5) times that of control individuals. The risk of suicide may be higher among women with HS.

19Nicotinic acetylcholine receptors are found on cells putatively implicated in the pathogenesis of HS. Nicotine has been shown to induce infundibular epithelial hyperplasia and hyperkeratosis, alter the cutaneous microbiome, stimulate release of TNF by keratinocytes and T-helper 17 cells, disturb polymorphic neutrophil granulocyte chemotaxis, and immunomodulate macrophage function.

20Five cross-sectional studies from Europe,,, South America, and Turkey observed significantly higher frequencies of self-reported smoking among patients with HS compared to control individuals, with prevalences in HS ranging from 17.9% to 88.9%. Two large retrospective studies in North America and Israel and a single-center case-control study also found a significant association between smoking and HS by using electronic records. In one of these, a 90% increase in risk (aOR, 1.9; 95% CI, 1.8–2.0) of new HS diagnosis was observed among smokers compared to nonsmokers, suggesting that smoking could be a risk factor for HS. Evidence supporting smoking cessation as a means to improve the disease course is limited.

21Patients with HS experience chronic pain and have physical, emotional, and psychological disease impact which may increase risk for substance use disorder (SUD).

22In a cross-sectional study in 32,000 patients with HS, the prevalence of SUD was 4.0%, compared to 2.0% in control individuals. The most common forms of SUD were alcohol and opioid use. Patients with HS had 1.50 times the adjusted odds of SUD (aOR, 1.50; 95% CI, 1.42–1.59). In a retrospective cohort study involving 20,000 patients with HS, the 1-year incidence of chronic opioid use among opioid-naive patients with HS was 0.3%, double that of control individuals. In adjusted analysis, patients with HS had 1.5 times greater risk (aOR, 1.5; 95% CI, 1.2–2.0) of developing chronic opioid use. In a single-center case-control study of 1800 patients with HS, diagnoses of alcohol dependence (4.2% vs 0.5%) and drug dependence (6.5% vs 0.5%) were more common in patients with HS compared to control individuals, although adjustment for comorbidities reversed or attenuated these associations.

23Both HS and polycystic ovary syndrome (PCOS) affect similar demographics, may be complicated by obesity and metabolic syndrome, and respond to antiandrogen agents.

24In a cross-sectional analysis involving 23,000 women with HS, the prevalence of PCOS was 9.0%, compared to 2.9% in control individuals. Women with HS had twice the adjusted odds of having PCOS (aOR, 2.14; 95% CI, 2.04–2.24). In other retrospective database studies evaluating various comorbid outcomes, the prevalences of PCOS among women with HS ranged from 0.8% to 4%. Across these studies, women with HS had 1.2 to 13.4 times the odds of having PCOS compared to control individuals.,,

25The biological link between HS and metabolic syndrome (MetS) may be explained by the downstream systemic effects of adipose tissue secretion of proinflammatory mediators in obesity along with insulin resistance in the setting of chronic inflammation. Impaired Notch signaling in HS may result in elevations of TNF and subsequent impairment of insulin signaling. Hyperinsulinemia in the setting of obesity may also lead to overactivation of mTORC1 signaling via insulin-like growth factor, resulting in insulin resistance.

26A higher prevalence of obesity among patients with HS compared to control individuals was observed across 7 studies, with prevalences ranging from 5.9% to 73.1%.,,,,,, In a meta-analysis of 8 studies, the adjusted pooled odds of obesity among patients with HS was 3.5 (95% CI, 2.2–5.4) times that of control individuals. Evidence supporting weight loss as a means of improving the disease course is limited.

27A higher prevalence of dyslipidemia among patients with HS compared to control individuals was observed across 4 studies, with prevalences ranging from 3.3% to 45.3%.–, Adjusted odds of dyslipidemia among patients with HS ranged from 1.4 to 4.1 times that of control individuals.– In a meta-analysis of 9 studies comprising 6174 patients with HS, the odds of hypertriglyceridemia and low high-density lipoprotein levels among patients with HS were 1.7 (95% CI, 1.1–2.5) and 2.5 (95% CI, 1.5–4.2) times that of control individuals, respectively.

28A higher prevalence of diabetes mellitus (DM) among patients with HS compared to control individuals was observed across 7 studies, with prevalences ranging from 7.1% to 24.8%.,,,,– In 2 meta-analyses of 12 and 7 studies, the pooled odds of DM among patients with HS were 2.17 (95% CI, 1.9–2.6) and 2.8 (95% CI, 1.8–4.3) times that of control individuals, respectively.

29Higher prevalences of MetS among patients with HS compared to control individuals were observed across 5 studies, with prevalences ranging from 10.4% to 50.6%.,,,, The pooled adjusted odds of MetS among patients with HS ranged from 1.8 to 2.2 times that of control individuals.,,

30Obesity and tobacco use are behavioral risk factors for hypertension that are associated with HS. Patients with HS had significantly higher prevalence of hypertension in 6 of 8 total studies addressing this relationship, with aORs ranging from 1.2 to 2.1.–,,,,, In these studies, the prevalence of hypertension among patients with HS ranged from 7.8% to 56.3%. In 1 of these studies, the risk of hypertension was lower in patients with HS (OR, 0.7; 95% CI 0.6–0.7] than control individuals, although data from this study were limited to single inpatient admissions and may not have included past comorbidity information.

31HS is associated with cardiovascular risk factors including obesity, smoking, DM, and dyslipidemia. Circulating TNF and IL-6 are elevated in HS and known to drive endothelial dysfunction, atherosclerosis, and thrombosis., As such, chronic systemic inflammation may support a biological link between HS and cardiovascular disease.

32The composite of myocardial infarction, cerebrovascular accident, and cardiovascular death, also referred to as major adverse cardiovascular events (MACE), are associated with HS. In a retrospective population-based cohort study, incidence rates of MACE among patients with HS and control individuals were 40 and 19 per 10,000 person-years, respectively. The adjusted incident risk of MACE among patients with HS was 1.5 (95% CI, 1.27–1.86) times that of control individuals, and the adjusted risk of cardiovascular death among patients with HS was 1.6 (95% CI, 1.2–2.1) times that of patients with psoriasis. In a single-center study, patients with HS had greater mean carotid intima-media thickness than control individuals. Patients with HS had carotid plaques more frequently, with a 3 times greater risk of carotid plaques (aOR, 3.0; 95% CI, 1.26–7.13]. In a prospective observational study, subclinical atherosclerosis was present in 30.6% of patients with HS compared to 16.1% of control individuals. The odds in patients with HS older than 40 years were 3.0 times greater than in control individuals (95% CI, 1.0–9.5). Resting heart rate, which is linked to all-cause and cardiovascular death, was associated with severe HS (adjusted mean difference vs control individuals, 2.9 beats/min; 95% CI, 0.7–5.1; P =.01).

33Ulcerative colitis (UC), CD, and HS are all chronic, recurrent, inflammatory disorders of the epithelia with the inhabitation of commensal flora. HS and CD are further characterized by suppuration and granulomatous inflammation, which may eventuate in fistula and sinus tract formation. Onset typically occurs in young adulthood. Spondyloarthropathy is also linked to all 3. These diseases may also share overlapping cytokine signatures with response to corresponding targeted therapies.

34The prevalence of CD among 50,000 patients with HS was 2%, compared to 0.6% among non–HS patients. The risk of CD among patients with HS was 3 times greater (aOR, 3.05; 95% CI, 2.87–3.25). In 3 other studies, prevalences of CD among patients with HS ranged from 0.2% to 0.8%.,– Among patients with HS, the adjusted odds of having CD were 1.2 to 2.0 times that of control individuals.,– The prevalences of UC among patients with HS ranged from 0.3% to 1.3%.,, In adjusted analyses from 3 population-based studies, patients with HS had 1.3 to 1.8 times the odds of UC compared to control individuals.,,

35Spondyloarthritis and HS share key inflammatory mediators including TNF, IL-1, and IL-17, which may suggest a biological link between these conditions. In 2 studies, the prevalences of spondyloarthritis among patients with HS were 0.3% and 28% compared with 0.2% and 2.6%, respectively, among control individuals., In 1 study of 1700 patients with HS, the prevalence of spondyloarthropathies was 52.5%, compared to 3% among control individuals. The adjusted odds of spondyloarthritis among patients with HS was 1.5–9.4 times greater.,

36Because HS involves the inframammary folds, groin, genitals, and buttocks, patients with HS may be at risk for sexual dysfunction (SD), including abnormal sexual function, impairment, and distress.

37Three prospective cross-sectional survey studies consistently showed significant differences in sexual health between patients with HS and control individuals using a variety of validated sexual health measures.– One study observed that both male and female patients with HS reported significantly lower sexual function compared to control individuals, as measured by the International Index of Erectile Function and Female Sexual Function Index. In a study involving more than 40,000 patients with HS, the 5-year cumulative incidence of SD was 1.7%, compared to 1.5% in control individuals. The risk of SD among patients with HS was approximately 1.4 (95% CI, 1.3–1.5) times that of control individuals, regardless of patient sex.

38The expression of amyloid precursor protein is increased in DS. In the epidermis, amyloid precursor protein plays a role in stimulating keratinocyte adhesion, migration, and proliferation. In this way, patients with Down syndrome (DS) may be prone to keratinocyte hyperproliferation and follicular plugging.

39In a cross-sectional study of nearly 12,000 patients with DS, the prevalence of HS was 2.1%, compared to 0.3% in control individuals. Patients with DS had 5 times the prevalence of HS (aOR, 5.24; 95% CI, 4.62–5.94) compared to patients without DS. More than 80% of patients with DS had their HS diagnosis by age 29 years. In a single-center study, the prevalence of HS among patients with DS was 24%, compared to 1.2% among control individuals.

40Conditions for which insufficient evidence exists to make recommendations on screening,,– or for which screening was not recommended–,,– are discussed in the Supplemental Materials.

41Several remaining knowledge gaps in our understanding of HS comorbidities are discussed in the Supplemental Materials.

42A number of comorbid conditions affect patients with HS and contribute to poor health and impaired quality of life, beyond the significant impact of the disease itself. These screening guidelines are intended to support health advocacy efforts along with comprehensive care strategies for patients with HS.