A case of guttate psoriasis during treatment with dupilumab

Dear Editor, A 40-year-old woman affected by severe atopic dermatitis (AD) was examined for an exacerbation of disease. The patient suffered from AD since the age of 2 years, and she had been treated with topical corticosteroids and calcineurin inhibitors, with partial clinical benefit. Her medical history revealed that she was also affected by allergic asthma and rhinitis since the age of 20 years. In addition, she underwent three cervical conizations in the last 2 years, due to high-grade cervical intraepithelial neoplasia (CIN III). Neither personal nor family history of other skin diseases was reported. At the time of first observation, the patient showed erythematous patches and multiple excoriations on the face, trunk, and extremities (EASI score = 22). Skin lesions were associated with severe pruritus and significant impact on patient's quality of life (NRS pruritus: 9/10; DLQI = 10). Treatment with cyclosporine and other systemic immunosuppressive drugs was ruled out in agreement with the gynecologist, and therefore dupilumab was started at scheduled dosage. After 8 weeks, the patient achieved a complete remission of AD lesions; related symptoms and quality of life drastically improved too (EASI = 2; NRS pruritus = 1/10; DLQI = 0). At Week 16 of dupilumab treatment, despite complete remission of AD, few scattered erythematous-squamous lesions were detected on the trunk and extremities (Figure 1). The patient referred that these lesions had appeared in the previous 2 weeks. Histopathological examination of a skin biopsy specimen obtained from a lesion on the trunk revealed parakeratosis, hyperkeratosis, acanthosis, dilated capillaries, and a lymphocytic infiltrate in the upper dermis (Figure 2). Based on clinical and histopathological features, guttate psoriasis was diagnosed. The patient did not show sign or symptoms of concomitant infections, and antistreptolysin O titer and pharyngeal swab resulted negative. Dupilumab was not interrupted and daily topical application of calcipotriol-betamethasone foam lead to complete remission of psoriatic lesions after 3 weeks. No other side effects were observed during treatment with dupilumab. The coexistence of AD and psoriasis in the same patient is not rare, in accordance with a common genetic background for these diseases, as shown by recent linkage and GWAS studies (Guttman, 2018; Weidinger, 2013). In our patient, guttate psoriasis, which developed 16 weeks after initiation of dupilumab treatment, may suggest the presence of a not yet identified infectious trigger exacerbating psoriasis. However, a triggering role of dupilumab in the development of psoriasis may not be ruled out,