(BQ) Part 1 book “Psoriasis” has contents: General description, psoriatic arthritis, therapy, effects of psoriasis on quality of life, psoriasis as a systemic disease, appendix, neurological disorders, gastrointestinal disease, psychiatric disorders, and other contents. | 73 4 PSORIATIC ARTHRITIS its cutaneous counterpart, psoriatic arthritis (PsA) has a broad range of clinical manifestations, complex pathophysiology, and deep impact on the quality of life of those afflicted. PsA provides a source of great scientific deliberation and clinical need. Recent advances in epidemiology, immunogenetics, and clinical classification have enhanced our understanding of this enigmatic and often debilitating joint disease. Discussions of treatment and quality of life considerations related to PsA can be found in the relevant chapters of this book and are not discussed here. L IKE GENERAL DESCRIPTION PsA joins a unique group of arthritic diseases unified by involvement of the joints and connective tissues of the spine (. spondyloarthropathy), as well as, in most cases, a negative serum test for the rheumatoid factor (RF) antibody to the constant portion of gamma immunoglobulin. A positive test for RF is one of the hallmarks of perhaps the best known of all inflammatory joint diseases, rheumatoid arthritis (RA). Clinicians should be aware, however, that 10–13% of patients with PsA are seropositive for RF1. Along with PsA, the socalled ‘seronegative spondyloarthropathies’ include ankylosing spondylitis, reactive arthritis (Reiter syndrome) and arthritis related to inflammatory bowel disease. Diseases of this group commonly produce signs and symptoms beyond the joints, such as lesions in the mucous membranes, inflammation of the iris and anterior chamber of the eye (. uveitis), aneurysm of aortic root, subclinical inflammatory bowel disease, and diarrhea2–4. Despite its inclusion among the seronegative spondyloarthopathies, PsA is unique. Experts in the field suggest that the spine is involved in only a minority of patients with PsA2 and, when it is, characteristics of symmetry, pain, and movement restriction differentiate the disease from the other spondyloarthropathies (see below). Indeed, many patients with PsA remain free of spinal
