Clinical and Epidemiological Characteristics of Hidradenitis Suppurativa Patients with Paradoxical Psoriasiform Reactions following Treatment with Adalimumab.

Introduction: Immunomodulation using TNF-α inhibitors (anti-TNF-a), especially adalimumab, is highly effective in the treatment of hidradenitis suppurativa (HS) in cases that are poorly controlled by conventional treatments. However, paradoxical psoriasis represents a peculiar type of psoriasis that may occur de novo or as the worsening of pre-existent psoriatic lesions during treatment with adalimumab. Case Presentation: We reported 4 cases of patients suffering from HS, who developed paradoxical psoriasis after treatment with adalimumab for their HS, analyzing their clinical and epidemiological characteristics. All 4 cases were middle aged, smokers, overweight or obese. Half of the patients were males (50%). All of them were classified as Hurley stage III, with a mean duration of HS of 20 years. Two patients had a family history of psoriasis. All 4 patients had been on at least 5 months of successful treatment with adalimumab before the onset of the lesions. Conclusions: Paradoxical psoriasis emerged in 4 patients who received at least 5-month regimen of adalimumab for long-lasting HS. Although different mechanisms have been hypothesized for such events, the exact underlying pathogenetic pathway remains unclear. Consistent reporting of such rare cases, and on a larger scale, is encouraged in order to enrich the available literature.