A case of dupilumab-induced psoriatic alopecia.

Dupilumab is a human monoclonal antibody, targeting the alpha subunit of the interleukin (IL)-4 receptor, shared by both IL-4 and IL-13 cytokines. Paradoxical reactions have been reported with its use, including psoriatic manifestations, but reports of associated psoriatic alopecia are sparse. We report a case of a 29-year-old man with severe atopic dermatitis from childhood who developed a psoriasiform rash and inflammatory alopecia affecting the scalp 7 weeks after the initiation of dupilumab. Histological features from a scalp biopsy were in keeping with psoriatic alopecia, including overlapping psoriasiform and spongiotic features, and the presence of peribulbar, deeper inflammation with eosinophils and plasma cells. Dupilumab was stopped and the scalp treated topically with steroids and ketoconazole shampoo. The patient was commenced on abrocitinib and within 6 months he had full regrowth of hair and his eczema was well controlled. Psoriatic alopecia has rarely been reported as a paradoxical reaction and can mimic the more common presentation of paradoxical alopecia areata. Histology is helpful in distinguishing these presentations, and cessation of the medication often leads to resolution. Paradoxical psoriatic manifestations are more common with tumour necrosis factor-α inhibitors, and a proposed mechanism for this reaction is a shift between the T helper (Th) 2 pathway to the Th1/Th17 pathway. Clinicians should be aware of this paradoxical reaction when prescribing dupilumab, and consider switching therapy to an alternative agent with a different mechanism of action should they encounter it.