Importance Hidradenitis suppurativa (HS) is relatively common, with the prevalence of 0.05% to 4.10%, yet many patients receive inadequate treatment. Objective To review the diagnosis, epidemiology, and treatment of HS with an emphasis on advances in the last 5 years. Evidence Review A literature search was conducted using PubMed, MEDLINE (Medical Subject Headings [MeSH]), and EMBASE to include recently published treatment studies (searched from September 1, 2011, to May 1, 2017). Reviews, guidelines, conference abstracts, and studies with less than 10 patients were excluded. Furthermore, internet searches for guidelines on hidradenitis suppurativa using Baidu, Bing, Google, and Qwant browsers were performed. Findings The diagnosis of HS is made by lesion morphology (nodules, abscesses, tunnels, and scars), location (axillae, inframammary folds, groin, perigenital, or perineal), and lesion progression (2 recurrences within 6 months or chronic or persistent lesions for ≥3 months). HS is more common than was previously thought based on epidemiological analysis (0.05%-4.10%). Disability from HS can be significant. Patients with HS may have significant comorbidities (eg, obesity, metabolic syndrome, diabetes, and arthritis) and increased all-cause mortality (incidence rate ratio, 1.35 [95% CI, 1.15-1.59]). Antibiotic treatment with combinations of clindamycin and rifampicin, or ertapenem followed by combination rifampicin, moxifloxacin, and metronidazole for 6 months is effective. Adalimumab is effective in a significant proportion of patients and treatment with IL-1 and IL-12 receptor subunit beta 1 (Rb1) antibodies may also be useful. Tissue-sparing surgical techniques and carbon dioxide laser treatments also are available, but the evidence on clinical outcomes with these approaches is limited. Conclusions and Relevance Hidradenitis suppurativa is more common than previously thought and may be treated by an array of pharmacological and surgical techniques. Hidradenitis suppurativa should be considered in the differential diagnosis of nodular lesions or sinus tracts present in the axillae, groin, perineal, and mammillary fold regions.

Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease of the hair follicle defined by recurrent nodules, tunnels (sinus tracts), and scarring involving the intertriginous regions.¹ The nodules may progressively expand to abscesses and subsequently rupture, causing suppuration and malodorous discharge.² The prevalence of HS has been estimated to be among 1% to 4% of the European populations.^3-5

Yeasts of the genus, Malassezia, formerly known as Pityrosporum, are lipophilic yeasts, which are a part of the normal skin flora (microbiome). Malassezia colonize the human skin after birth and must therefore, as commensals, be normally tolerated by the human immune system. The Malassezia yeasts also have a pathogenic potential where they can, under appropriate conditions, invade the stratum corneum and interact with the host immune system, both directly but also through chemical mediators. The species distribution on the skin and the pathogenetic potential of the yeast varies between different Malassezia related diseases such as head and neck dermatitis, seborrheic dermatitis, pityriasis versicolor, and Malassezia folliculitis. The diagnostic methods used to confirm the presence of Malassezia yeasts include direct microcopy, culture based methods (often a combination of morphological features of the isolate combined with biochemical test), molecular based methods such as Polymerase Chain Reaction techniques, and Matrix Assisted Laser Desorption/Ionization—Time Of Flight mass spectrometry and the chemical imprint method Raman spectroscopy. Skin diseases caused by Malassezia are usually treated with antifungal therapy and if there are associated inflammatory skin mechanisms this is often supplemented by anti-inflammatory therapy. The aim of this paper is to provide an overview of Malassezia related skin disease, diagnostic methods and treatment options.

In recent years, cases involving terbinafine-resistant Trichophyton isolates have been reported increasingly, particularly in India. We present 14 cases of terbinafine treatment failure in Trichophyton -infected Danish patients due to acquired resistance. Patients infected with Trichophyton rubrum ( n = 12) or Trichophyton interdigitale ( n = 2) with elevated terbinafine MICs during 2013–2018 were included.