Introduction

Behçet's disease (BD) is an auto-inflammatory disorder, characterised by recurrent oral aphtosis, genital ulcers, uveitis and pustular skin lesions.1 Associated cutaneous diseases include Sweet's syndrome,2 erythema nodosum and pyoderma gangrenosum.3 Next to BD, both psoriasis and hidradenitis suppurativa (HS) are clear neutrophilic and interleukin (IL)-17-based diseases, suggesting a pathomechanistic overlap.4^–7 However, these diseases rarely co-occur.4 Ustekinumab (anti-p40 mAb), an effective biological treatment for psoriasis, might be effective in BD by interfering with the IL-17 signalling via IL-23 blockage. We present a 39-year-old Caucasian woman in whom the combination of BD, psoriasis and HS was successfully treated with ustekinumab.