Pembrolizumab-induced plaque psoriasis successfully treated with risankizumab in a patient with stage IV cutaneous melanoma.

Immune checkpoint inhibitors, such as pembrolizumab and nivolumab, are monoclonal antibodies that block programmed cell death 1 (PD-1) expressed on activated CD8+ T cells and play a crucial role in the treatment of advanced melanoma. With the wide adoption of these therapies, a range of cutaneous adverse effects has been reported, such as flares of plaque psoriasis, but no specific guidelines regarding the treatment are available. We present the case of a 28-year-old male diagnosed with stage IV non-BRAFV600E mutated melanoma in 2014. After the surgery and the failure of ipilimumab and IL-2, he started immunotherapy with pembrolizumab. One month after the start of the therapy, he came to our department showing a severe flare of plaque psoriasis with a body surface area of 40% and a Psoriasis Area and Severity Index (PASI) of 28. Given the severity of the clinical picture and the contraindications to conventional systemic therapy, we decided to start biological treatment with risankizumab, an anti-IL-23 inhibitor. After just the induction phase, he showed almost skin clearance obtaining a reduction of more than 90% of the baseline PASI. Our patient's rapid response to risankizumab enabled us to continue immunotherapy with pembrolizumab. The recognition of cutaneous signs of toxicity related to such drugs for advanced melanoma is of primary importance to start the correct treatment and continue the immunotherapy when possible.