LAUSR

Biological drugs can induce paradoxical reactions through the blockade of immunological targets as a result of a cytokine imbalance (Munera-Campos, Ballesca, Richarz, Ferrandiz, & Carrascosa, 2019). We have recently described the possible occurrence of eczematous eruption (EE) during anti-interleukin (IL)-17 treatment of psoriasis (Napolitano et al., 2019) as well as psoriasiform eruption during dupilumab therapy for adult atopic dermatitis (AD) (Napolitano, Scalvenzi, Fabbrocini, Cinelli, & Patruno, 2019). Herein we report an EE (AD-like) in a psoriasis patient receiving anti-IL-17 (ixekizumab) treatment completely cured with dupilumab. A 62-year-old man with psoriasis presented with a 2-month history of a diffuse pruritic rash. The patient had personal history of AD in childhood with remission during adolescence. He was affected by psoriasis since the age of 25 years. Previous psoriasis therapies included phototherapy, methotrexate, adalimumab, and etanercept without consistent improvement. Cyclosporine, even if effective, was discontinued after 5 months due to the onset of hypertension and moderate renal failure. The patient was then treated with ixekizumab (5 months before the onset of the pruritic rash) achieving an almost complete response (PASI decreased from 14.8 at baseline to 0.8 after 20 weeks). Physical examination revealed diffuse erythematous papules, excoriation, and serous exudation, especially on the trunk and upper and lower limbs (Figure 1). Blood test results were within the normal range except for immunoglobulin E (1,400 kU/L, normal value <140). Spongiosis, edema in upper dermis, and perivascular lymphocytic infiltrate were identified through skin biopsy sent for histological examination. Despite oral prednisone therapy (0.5 mg/kg) and discontinuation of ixekizumab, clinical manifestations and itching persisted over time. Based on the clinical and medical history and histological examination, AD-like eruption was diagnosed and a treatment with dupilumab (600 mg induction dose and then 300 mg every 2 weeks) was started, with improvement within 2 weeks and complete clearance sustained up to 22 weeks follow-up (Figure 2). Biological therapies induce changes in the cytokine expression which may direct cutaneous immune response to an eczematous phenotype in predisposed individuals. Psoriasis and AD are characterized by an imbalance in the T helper (Th)1/Th2 immune response, with Th1 being more prominent in psoriasis and Th2 in AD. Probably, during biologic therapies, when the Th1 response is blocked or decreased, the Th2 balance will in