Hidradenitis suppurativa: current progress and future questions.

Hidradenitis suppurativa (HS) is a chronic, destructive, debilitating inflammatory skin disease characterized by recurrent, painful, deep-seated nodules and/or abscesses in intertriginous areas.1 It is also relatively common,with a reported prevalence as high as 1% to 4%.2,3 Nevertheless, HS has historically been an orphan disease, unclaimed by any specialty, owing, perhaps largely, to the treatment challenges it poses for physicians and the resulting nonadherence on the part of patients. Recently, however, there has been a surge in HS interest, as evidencedby the substantial increase innumberofHSpublications listed inPubMed, fromaround30 in 2005 to approximately 100 in 2013. This increased activity highlights the possibility thatmore effective treatment forHS is at hand. Today, we have new therapies, new applications of existing therapies, and a growing understanding of the biology and genetics of both the disease and its spectrum of presentations. One obvious but important area of inquiry that derives from this recent progress is the examination of common HS comorbidities. It has long been established that patientswith HS are more likely to be obese than the general population. Therehavealsobeen fascinating syndromesdescribed that includeHSandthat clearlydemonstratean important roleof systemic inflammation. So, givenour field’s highly successful exploration of associations of metabolic syndrome (MetS) and other comorbidities inpsoriasis, an approach to evaluatingHS is well established. There should be, however, some real differences between the HS and psoriasis populations. Psoriasis, at least in most of our studies ofmoderate to severedisease, affectsmen in their 40s. In contrast,HS is disease of youngerwomenwho, basedoncomparisonsofmoderate toseverecases in largeclinical trials in both disease categories, may carry a higher obesityburden.Thesedemographicdifferences alone should substantially affect the risk of myocardial infarction or other cardiovascular diseases across the 2 groups. As part of this ongoing line of inquiry, in the present issue of JAMADermatology,Miller et al4 report onHSand its associationwithMetS.Theircross-sectionalanalysis includesdatafrom 32 hospitalized patients with HS, 326 population-based individualswithHS, and 14 851 population-based personswithout HS inDenmark. Thehospital caseswerephysician verified; the population caseswere identified based on questionnaires; and the non-HS controls were from the general Danish population. Consistent with previous studies, the vast majority of patients with HSwerewomen andwere current or former smokers.5 The authors define MetS according to amodified version of the National Cholesterol Education Program Adult Treatment Panel III criteria,6 which involves 4 key parameters: abdominal obesity, dyslipidemia, hypertension, and diabetes. They found a significant correlation in both the hospital and populationHSgroupswithMetS,diabetes, general obesity, abdominal obesity, and low levels of high-density lipoprotein. TheassociationbetweenHSandhypertriglyceridemiawas significant only for the population HS group, whereas the association betweenHS andhypertensionwas significant only for the hospital HS group. This finding is perhaps not surprising given the known obesity in the hospitalized population. When the authors adjusted for patient obesity or inflammatory load (measuredbyC-reactiveprotein [CRP] levels), the strength of the association between HS and MetS was reduced but remained significant. The median CRP level was higher inpersonswithHS (5.1 and2.1mg/L for thehospital and population groups, respectively) than in the non-HS population (1.4mg/L). Interestingly, the association betweenHSand MetSor individualMetSparameterswasnot influencedby the degree of HS severity, with the exception of general obesity. This study has several strengths that distinguish it from others examining the association of HS and MetS. It evaluatesbothhospitalizedandpopulation-basedpatientswithHS; it includes a largenumber of population-based cases and controls; and it analyzes the effects of possible confounding factors including inflammatory load (asmeasured by CRP level), physical activity, diet, and alcohol consumption.While activity level, diet, and alcohol consumption were not associated with HS, increased CRP level was associated with both HS andMetS. Two recent studieshave similarly demonstrated a linkbetween HS and MetS. In 2012, Sabat et al3 observed a significant correlationbetweenHSandMetS inahospital-basedcasecontrol studyof80patientswithHS. Similarly, earlier this year ina retrospectivechart review,Goldetal7 foundahigherprevalence of MetS in 366 patients with HS than in a control population of clinic patients. However, in contrast to the establishedassociationbetweenhigherobesity levelsandworsening HS disease severity, neither study observed a correlation between HS severity and MetS.3,7 TheassociationofHSwithobesity iswell established.However, this novel association between HS and MetS, of which obesity is but 1 component, highlights the potential risks of MetS and raises intriguing questions: What level of systemic inflammation do patients with HS experience? Is this inflammation a cause or an effect of the disease, and howmuch of it Related article page 1273 Opinion