“…The above-mentioned scoring systems, however, could not reflect the wider clinical spectrum of HS and the associated comorbidities, especially in the syndromic forms; for these reasons, considering the clinical variability of the disease and the lack of a homogeneous classification, Van der Zee et al [ 28 ] proposed to classify HS in six clinical phenotypes: (i) regular type, which represents the typical lesions described above, (ii) frictional furuncle type, characterized by nodules and abscesses in friction areas (buttocks, legs, and abdomen), which rarely evolve into fistulas, (iii) scarring folliculitis type, in which classical superficial lesions (Hurley stage I) are frequently followed by cribriform scarring and pseudocomedones, (iv) conglobate type, in which cyst formation and acne conglobata predominates on the face and upper back with a strong familiar history, (v) syndromic type in patients with concomitant diseases such as inflammatory bowel disease (IBD), arthritis, and autoinflammatory syndromes, and finally, (vi) ectopic type, in which the main area involved is the face [ 30 ]. Subsequently, Dudnik et al [ 31 ], based on real-life observation on a Dutch cohort of patients, suggested that the ectopic and syndromic phenotypes were not specific, lacking distinctive clinical features and could be categorized as one of the other phenotypes; interestingly, a positive family history did not differ between the phenotypes. Frew et al [ 32 ] assessed the inter-rater reliability of HS phenotypes described in the literature and based on genotype-phenotype correlation and proposed a revision of the classification limiting it into a: (i) typical HS, corresponding to the regular type, (ii) atypical HS, including scarring folliculitis and conglobate types, and (iii) syndromic HS [ 32 ].…”