Psoriatic arthritis is a long-term inflammatory arthritis that occurs in people affected by the autoimmune disease psoriasis. The classic feature of psoriatic arthritis is swelling of entire fingers and toes with a sausage-like appearance. This often happens in association with changes to the nails such as small depressions in the nail, thickening of the nails and detachment of the nail from the nailbed. Skin changes consistent with psoriasis frequently occur before the onset of psoriatic arthritis but psoriatic arthritis can precede the rash in 15% of affected individuals. It is classified as a type of seronegative spondyloarthropathy.