Vitiligo may thus emerge and/or progress during treatment with various biological agents, mainly TNFα inhibitors and could be a new paradoxical skin reaction. De novo vitiligo displays a favourable outcome when maintaining the biological agent, whereas the prognosis seems worse in cases of pre-existing vitiligo.

first treatment, and, following her second treatment, went into clinical remission. She was still in remission when discharged from follow-up 1 year after her fourth treatment.Although we did not manage to induce such a prolonged period of remission in the other two patients, both had a good response to the BTXA treatments, and they experienced disease-free intervals of 5-6 months after treatment.The exact mechanism by which BTXA affects the disease process in HS is unclear. The moist environment resulting from entrapped sweat in the axilla and groin provide ideal conditions for the flourishing of bacteria. This may well be compounded by the presence of apocrine gland secretions, which form a rich substrate for bacterial growth. The antiperspirant effect of BTXA would then reduce the population of skin flora, subsequently reducing the inflammatory stimulus for HS.A second possibility is that BTXA switches off the function of the whole pilosebaceous unit and apocrine secretions, thus preventing the rupture and spread of follicular material through the dermis, which would usually result in further inflammation and sinus tract formation.In conclusion, the positive clinical results from our practice demonstrate the potential for use of BTXA in the treatment of HS. Further research will need to be carried out to establish the effectiveness of the treatment in a larger cohort of patients with this highly debilitating disorder.

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