 Beta defense in 2, BD2, is a protein that is present in the skin and mucous membranes of healthy individuals. It has been shown to be associated with psoriasis severity, but its role in psoriatic arthritis, PSA, remains unclear. A recent study investigating the efficacy of succukinumab, a drug used to treat PSA, revealed that patients with high levels of BD2 at baseline had better clinical responses than those with low levels. This suggests that BD2 may serve as a potential biomarker for predicting clinical response to this type of treatment. This article was authored by Richard M. Zegel, Mark van der Mulebroek, Mathias Cardner, and others.