Inflammatory arthritis following ustekinumab treatment for psoriasis: a report of two cases. 
Psoriasis is a chronic inflammatory skin condition, characterized by T-helper (Th) 1 and Th17 cell activation.  Ustekinumab is a fully human immunoglobulin G1κ monoclonal antibody that targets the common p40 subunit that is shared by both interleukin (IL)-12 and IL-23, consequently inhibiting T-cell differentiation along both Th1 and Th17 pathways.  This is a report of two patients who developed psoriatic arthritis during ustekinumab treatment for psoriasis.  Neither patient had a personal or family history of arthritis.