Palmoplantar pustulosis induced by infliximab in ankylosing spondylitis and successful treatment with ustekinumab: a case report and literature review

New onset or exacerbated psoriatic lesions in patients treated with TNF-α-inhibitors (TNFi) have been frequently reported in literature. We describe a patient with ankylosing spondylitis (AS) who developed a very severe palmo-plantar pustulosis (PPP) after the third infusion of infliximab, whose administration was consequently stopped. PPP was refractory to both local and systemic therapies, and shortly after discontinuation of TNFi the patient experienced a severe flare of AS, poorly responsive to the administration of non-steroidal anti-inflammatory drugs. Ustekinumab led to a rapid and persistent remission of both PPP and SA. Review of the literature was focused on the identification of cases of PPP without concomitant psoriasis developed after TNF-α-inhibitors. Main pathogenetic mechanisms that link the appearance of PPP to the use of TNFi and the difficulties in PPP treatment are discussed.