Background:Pityriasis rubra pilaris is a rare, chronic erythematous squamous disorder of unknown etiology. The disease is characterized initially by small follicular papules that coalesce into yellowish pink scaly plaques, palmoplantar keratoderma, diffuse furfuraceous scale of the scalp, and frequent progression to exfoliative erythroderma. Generally it is difficult to discern pityriasis rubra pilaris from other skin conditions but key-clinical features help in the diagnosis such as "islands" of spared skin within generalized erythroderma, follicular keratotic plugs, and an orange hue of the involved skin. Treatment options include topical vitamin D analogues, keratolytics, systemic acitretin, methotrexate, cyclosporine, azathioprine, fumaric acid esters, phototherapy, and anti-TNFα agents. Cases, of pityriasis rubra pilaris, successfully treated with a short-course ustekinumab therapy, have been reported.Main observations:We report a 31-year-old man with pityriasis rubra pilaris, refractory to conventional treatments, successfully treated with ustekinumab monotherapy for over 64 weeks.After failing conventional systemic agents (cyclosporine, aciretin and methotrexate), ustekinumab 45 mg has been prescribed, with the same dosing regimen as in psoriasis. The patient improved dramatically within 4 weeks of the first injection, with markedly less erythema and pruritus. Long-term control of the disease of the disease was achieved (64 weeks of treatment).Conclusion:We report this case in order to show the striking and rapid efficacy of ustekinumab in reducing the signs and symptoms of the disease. Complete remission was achieved after the third injection, but also a long-term control of the disease. The therapy was well-tolerated in our patient and no adverse events occurred.