Drug-induced psoriasiform alopecia associated with interleukin-17 inhibitor therapy

Drug-induced psoriasiform alopecia is an increasingly recognized form of alopecia mostly reported in association with TNF-alpha inhibitors. However, drug-induced psoriasiform alopecia in association with IL-17A inhibitors has not been described. We present a 62-year-old woman with severe psoriasis who developed new psoriatic plaques on the scalp with alopecia after initiating ixekizumab (anti-IL-17A). Scalp biopsy specimens revealed a non-cicatricial alopecia with increased telogen/catagen follicles, atrophy of the sebaceous glands, peribulbar and perifollicular inflammation with frequent lymphocytes, plasma cells, eosinophils, psoriasiform dermatitis, and lack of intra-corneal or intra-epidermal neutrophils. Overall, the clinical and histopathologic findings were most compatible with a drug-induced psoriasiform alopecia in association with IL-17A inhibitor therapy. Our case shows that drug-induced psoriasiform alopecia can paradoxically occur in patients on IL-17A inhibitor therapy and contributes to the growing list of cutaneous eruptions associated with biologic agents.