Successful treatment of PD1-inhibitor induced psoriasiform dermatitis using IL-17 blockade without compromising immunotherapy efficacy.

Introduction: Pembrolizumab is a monoclonal PD-1 inhibitor used in the treatment of lung cancer in addition to several other malignancies. Psoriasiform dermatitis is a well-documented adverse effect.

Case report: We present a 68 year-old-male with a 50-year smoking history and a 30-year remote history of plaque psoriasis, limited to the knees and elbows, who presented with metastatic non-small cell lung cancer. He was started on a chemotherapy regimen of carboplatin, paclitaxel, and pembrolizumab. One month later, he presented to dermatology with diffuse erythematous scaly papules coalescing into plaques on 80% of body surface area (BSA).

Management & outcome: Pembrolizumab treatment was paused. The patient was prescribed triamcinolone 0.1% twice daily, but still had significant BSA at one-month and was started on an Il-17 inhibitor, ixekizumab, clearing the psoriasiform dermatitis. He was rechallenged with pembrolizumab every 3 weeks and repeat PET/CT demonstrated excellent tumor response.

Discussion: This case prompted a literature review to further characterize the use of IL-17 inhibitors for psoriasiform dermatitis in the setting of ICI therapy. All six cases demonstrated improvement of psoriasiform dermatitis, with two cases showing partial response and four cases showing complete resolution. In three of the six cases, the patients exhibited clinical response to the primary malignancy after rechallenging with ICI, while remaining on an IL-17 inhibitor. Our case, in conjunction with the other reported cases, seems to suggest that IL-17 blockade can maintain a fine balance in this challenging clinical scenario by treating psoriasiform dermatitis without compromising the efficacy of immunotherapy.