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  • Psoriatic arthritis is a progressive inflammatory musculoskeletal disease occurring in about a third of people with psoriasis.

  • Psoriatic arthritis is underdiagnosed.

  • Clinical presentation is heterogeneous and variably includes the following manifestations: peripheral arthritis, spondyloarthritis (inflammatory arthritis of the spine), enthesitis (inflammation at the insertion sites of ligaments and tendons onto bone), and dactylitis (full-thickness inflammation of digits and toes).

  • Associated extramusculoskeletal manifestations in addition to skin and nail psoriasis are inflammatory eye disease and inflammatory bowel disease.

  • Several genetic risk factors have been identified for psoriatic arthritis.

  • Serology for the rheumatoid factor is usually negative and inflammatory markers may be normal.

  • Prompt recognition, pharmacologic treatment, and disease monitoring are necessary to prevent damage and improve long-term outcomes for psoriatic arthritis.

Psoriatic arthritis (PsA) was first linked to psoriasis in 1818 by French dermatologist Jean L. M. Alibert while caring for patients with chronic diseases at Hopital Saint-Louis in Paris. He noticed the association of psoriasis with inflammatory joint disease flares. The first case series was described by French dermatologist Charles Bourdillon in his doctoral thesis in 1888 and included descriptions of the PsA characteristic involvement of the distal interphalangeal joints as well as the disability potentially associated with PsA.1,2

Almost a century later, in 1973 John H. M. Moll and Verna Wright characterized PsA in great clinical detail and developed the first classification rule for PsA3 consisting of inflammatory arthritis compatible with a PsA phenotype, psoriasis, and seronegative status for the rheumatoid factor. Several other classification schemes were developed. The Classification criteria for PsA (CASPAR)4 are now the most widely accepted and define inclusion of participants in PsA clinical trials (Table 65-1).

Table 65-1The Classification Criteria for PsA (CASPAR)

Much progress has been made in recent years in understanding PsA pathophysiology through the discovery of specific molecular pathways involved in disease initiation and progression. A number ...

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