[Cutaneous side effects of biologics: an important topic also in occupational dermatology].

A 42-year-old machinist suffered from ankylosing spondylitis since 2009. This had been treated with adalimumab 40 mg subcutaneous (s.c.) every two weeks since 2021. Approximately four years later, he developed erythema and pustules on his palms and soles of the feet. Palmoplantar pustular psoriasis and psoriasis vulgaris were diagnosed. His treatment was changed to secukinumab 150 mg s.c. every four weeks and his skin condition improved slightly. This case demonstrates the importance of considering adverse reactions to biologics in refractory palmoplantar psoriasis, even after years of treatment.