Psoriatic arthritis: a diagnostic challenge?

Psoriatic arthritis (PsA) is an inflammatory arthritis associated with psoriasis vulgaris. Making the diagnosis is not trivial even today. In contrast to older data, relatively high rates of disease progression and joint damage have been found in recent trials. Whether this originates from erroneously included patients with rheumatoid arthritis or true severity of PsA needs to be confirmed. The ClASsification criteria for Psoriatic Arthritis criteria are now widely accepted and used in the setting of clinical studies. Their further validation and development is conducted by Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA). Correct diagnosis and classification is a prerequisite for valid conclusions from therapeutic and prognostic clinical trials and optimal care for individual patients. This article reviews clinical presentation, diagnostic tools, classification criteria, differential diagnosis and treatment options in PsA.