New onset or transition of disease state of psoriatic arthritis during treatment with ustekinumab: A single-center retrospective study.

Ustekinumab (UST) is a treatment option for psoriatic arthritis (PsA), but recent observations indicate that some psoriatic patients may experience new onset of PsA or worsening of pre-existent PsA. We retrospectively analyzed all cases of psoriasis vulgaris (PsV) and PsA treated with UST in our facility between 2011 and 2015. PsA developed in eight out of 179 PsV patients, mostly later than 8 months after initiation of UST. It was generally not severe, and none had received tumor necrosis factor (TNF)-α inhibitors previously, indicating that the possibility of unmasking pre-existing subclinical arthritis is minimal. The eruptions were well controlled at the time of the onset of arthritis in most cases. Interestingly, those who developed arthritis showed a significantly lower body mass index. Regarding pre-existing PsA, nine PsA patients received UST, and at least partial improvement of PsA could be achieved in two out of three bio-naive and three out of six bio-switched patients from TNF-α inhibitors. PsA was largely more refractory to UST than the eruptions. Altogether, our present study is in agreement with the notion that UST may be less efficient than TNF-α inhibitors for PsA. While UST cannot fully prevent new development of PsA, it is unlikely that UST increases the risk of new onset of PsA as a paradoxical adverse reaction.