musculoskeletal and connective tissue disorders
Psoriatic Arthritis
Diagnosis of Psoriatic Arthritis
Clinical evaluation Rheumatoid factor (RF) Psoriatic arthritis should be suspected in patients with both psoriasis and arthritis. Because psoriasis may be overlooked or hidden or develop only after arthritis occurs, psoriatic arthritis should be considered in any patient with seronegative inflammatory arthritis, particularly with involvement of distal interphalangeal joints, asymmetric or lower spine involvement, or presence of enthesitis and/or dactylitis: these patients should be examined for psoriasis and nail pitting and should be questioned about a family history of psoriasis. Patients suspected of having psoriatic arthritis should be tested for RF. Occasionally, RF test results can be positive. However, anticyclic citrullinated peptide antibodies (anti-CCP) are highly specific for Rheumatoid Arthritis (RA) and are only rarely present in psoriatic arthritis. Psoriatic arthritis is diagnosed clinically and by excluding other disorders that can cause such similar manifestations. X-ray findings common in psoriatic arthritis include distal interphalangeal joint involvement; resorption of terminal phalanges and cupping of proximal phalanges; arthritis mutilans; and extensive destruction, proliferative bone reaction, a sausage-like appearance to digits, and dislocation of large and small joints. The main distinguishing features from rheumatoid arthritis, in addition to the presence of psoriasis, include findings of dactylitis, joint asymmetry, distal interphalangeal and sacroiliac joint involvement, and more prominent enthesitis. 