Difficult to Treat and Refractory to Treatment in Psoriatic Arthritis.

Psoriatic arthritis (PsA) is a complex and chronic inflammatory condition in which the achievement of the best possible disease control has been proposed as the treatment target, which includes the possibility of reaching remission in all disease domains. However, due to the complexity of this multidomain disease, some patients may still have high disease activity in one or more domain and a high burden of disease, potentially leading to various treatment changes and to difficulty with the overall management. In this paper, we overview the concept of patients with difficult-to-treat PsA and the concept of patients with refractory-to-treatment PsA by providing a distinction between these two concepts and the possible implication for the management of patients with PsA.