Can retinoids flare hidradenitis suppurativa? A further case series

Linked article: Gallagher CG et al. Clin Exp Dermatol 2019; https://doi.org/10.1111/ced.13944. We read with great interest the recent article by Gallagher et al.1 in Clinical and Experimental Dermatology, concerning eight patients with severe acne who were treated with isotretinoin and developed hidradenitis suppurativa (HS). In a similar manner, we have had patients who experienced flares of HS when treated with retinoids. We report three cases of patients with moderate to severe HS localized in their axillae and groins. All three patients were male, current smokers, without any comorbidity, and with a mean age of 43 years and a mean BMI of 25.8. Additionally one patient had a family history of HS (Table 1). Patient demographics, clinicial characteristics and therapy Patient demographics, clinicial characteristics and therapy Patient 1 was a 31‐year‐old man with HS since the age of 14 years. During treatment with isotretinoin, he experienced progressive worsening of HS with increased suppurations and pain, so retinoid treatment was stopped and he was subsequently treated successfully with moxifloxacin plus a combination of rifampicin and metronidazole. Patient 2 was a 45‐year‐old man with severe HS that was partially controlled by adalimumab 40 mg weekly. He was started on concurrent acitretin. However, during the course of therapy, the patient developed significant aggravation of both symptoms and suppuration. Consequently, acitretin was stopped and corticosteroids were prescribed in association with adalimumab. Patient 3 was a 54‐year‐old man with severe HS unresponsive to first‐line oral antibiotics. He was started on acitretin, but this was followed by a marked worsening of his HS. Therefore, retinoid was stopped and the patient began therapy with corticosteroid and fluoroquinolones. Both acne and HS are diseases of the follicle apparatus, and owing to this similarity retinoids were proposed as treatments for HS also,1 although in HS, the sebaceous glands seem to be reduced or absent.2 Both acitretin and isotretinoin have antiacne and antisebum effects, caused by inhibition of sebocyte proliferation, although the potency of acitretin is much lower than that of isotretinoin.3 Nevertheless, acitretin has marked antiproliferative and anti‐inflammatory effects, suggesting a possible explanation for its higher efficacy than isotretinoin in HS treatment. We find interesting the proposal by Gallagher et al. that the low number of sebaceous glands may explain the poor effectiveness of isotretinoin in HS.1 In addition, we share their hypothesis that in some cases isotretinoin, and maybe also acitretin may aggravate HS through their mechanism of action, although an initial increase of HS breakouts may be expected at the beginning of the treatment with retinoids, as also happens in acne. Further randomized control trials are necessary to confirm these observations. We thank the Editor of CED and the authors for this article, which has the potential of inciting debate on these evidently important issues. Conflict of interest: the authors declare that they have no conflicts of interest.