Case of pityriasis rubra pilaris progressed to generalized erythroderma following blockade of interleukin-17A, but improved after blockade of interleukin-12/23 p40.

We report herein a case of a 72-year-old man with pityriasis rubra pilaris (PRP) that was refractory to conventional therapies. His skin lesions progressed to generalized erythroderma despite anti-interleukin (IL)-17A antibody therapy. Topical corticosteroids, emollients, systemic retinoid, methotrexate, cyclosporin and phototherapy yielded no therapeutic response. However, blockade of IL-12/23 p40 dramatically improved his cutaneous lesions. Complete remission was achieved 4 weeks after the first injection of ustekinumab and maintained for more than 48 weeks. Our data indicate that IL-12 was associated with the onset of PRP in this patient, rather than IL-23. IL-12 is critical for the differentiation of T-helper (Th)1 cells. Thus, the Th1 pathway may be associated with the onset of PRP.