[Psoriatic arthritis: what the dermatologist needs to know, part 1].

Psoriatic arthritis is defined as inflammatory arthritis occurring in patients with psoriasis and is classified as a seronegative spondyloarthropathy associated with human leukocyte antigen B27. Between 25 and 35% of patients with psoriasis go on to develop psoriatic arthritis during the course of their disease. Given that the skin is affected before the joints in most cases, the dermatologist must be able to recognize the signs and symptoms in order to make a diagnosis and start the most appropriate treatment. This review aims to cover key aspects of the initial diagnostic workup and clinical evaluation. It examines the epidemiology, pathogenesis, and manifestations of psoriatic arthritis, as well as the complementary tests and diagnostic tools the dermatologist should be aware of in order to make the correct diagnosis.