Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 20-32: Psoriatic Arthritis + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ Psoriasis precedes arthritis in 80% of cases Arthritis usually asymmetric, with "sausage" appearance of fingers and toes (dactylitis); polyarthritis that may resemble rheumatoid arthritis Sacroiliac joint involvement common Radiographic findings Osteolysis Pencil-in-cup deformity Relative lack of osteoporosis Bony ankylosis Asymmetric sacroiliitis Atypical syndesmophytes +++ General Considerations ++ Although psoriasis usually precedes the onset of arthritis, arthritis precedes (by up to 2 years) or occurs simultaneously with the skin disease in approximately 20% of cases The patterns or subsets of psoriatic arthritis include the following: A symmetric polyarthritis that resembles rheumatoid arthritis; usually, fewer joints are involved than in rheumatoid arthritis An oligoarthritis that may lead to considerable destruction of the affected joints A pattern of disease in which the distal interphalangeal (DIP) joints are primarily affected Early, this may be monarticular Joint involvement is often asymmetric Pitting of the nails and onycholysis frequently accompany DIP involvement A severe deforming arthritis (arthritis mutilans) with osteolysis A spondylitic form in which sacroiliitis and spinal involvement predominate; 50% of these patients are HLA-B27-positive + Clinical Findings Download Section PDF Listen +++ ++ Arthritis is at least five times more common in patients with severe psoriatic skin disease than in those with only mild skin findings Occasionally, however, patients may have a single patch of psoriasis (typically hidden in the scalp, gluteal cleft, or umbilicus) and are unaware of its presence Psoriatic lesions may have cleared when arthritis appears; in such cases, the history is most useful in diagnosing previously unexplained cases of mono- or oligoarthritis Nail pitting is sometimes a clue "Sausage" swelling, or dactylitis, of one or more digits is a common manifestation of enthesopathy in psoriatic arthritis + Diagnosis Download Section PDF Listen +++ +++ Laboratory Findings ++ Elevated erythrocyte sedimentation rate Rheumatoid factor and anti-CCP antibodies are not present Uric acid levels May be high, reflecting the active turnover of skin affected by psoriasis There is a correlation between the extent of psoriatic involvement and the level of uric acid, but gout is no more common than in patients without psoriasis Desquamation of the skin may also reduce iron stores +++ Imaging ++ Radiographic findings are most helpful in distinguishing the disease from other forms of arthritis MRI is more sensitive than plain radiographs in detecting axial abnormalities, especially in the first few years of disease onset Ultrasonography and MRI are more sensitive than conventional radiographs in detecting peripheral arthritis, enthesitis, and dactylitis + Treatment Download Section PDF Listen +++ ++ A TNF inhibitor biologic agent is recommended as first-line agent If TNF inhibitor is contraindicated or not tolerated, methotrexate (or other oral small molecule agent, such as leflunomide, sulfasalazine, cyclosporine, or apremilast) may be effective Patients who do not respond to TNF inhibitors or oral small molecule agents can be treated with Ustekinumab, a monoclonal antibody that inhibits IL-12 and IL-23 or Secukinumab or ixekizumab, which inhibit IL-17 Tofacitanib (Jak-stat inhibitor) and abatacept (CTLA4 inhibitor) may be options when other therapies fail Corticosteroids are less effective in psoriatic arthritis than in other forms of inflammatory arthritis and may precipitate pustular psoriasis during tapers + References Download Section PDF Listen +++ + +Brahe CH et al. Retention and response rates in 14 261 PsA patients starting TNF inhibitor treatment—results from 12 countries in EuroSpA. Rheumatology (Oxford). 2020 Jul 1;59(7):1640–50. [PubMed: 31665497] + +Gladman DD et al. Ixekizumab and complete resolution of enthesitis and dactylitis: integrated analysis of two phase 3 randomized trials in psoriatic arthritis. Arthritis Res Ther. 2019 Jan 29;21(1):38. [PubMed: 30696483] + +Singh JA et al. Special article: 2018 American College of Rheumatology/National Psoriasis Foundation guideline for the treatment of psoriatic arthritis. Arthritis Care Res (Hoboken). 2019 Jan;71(1):2–29. [PubMed: 30499259] + +Zhang AD et al. Treat to target in psoriatic arthritis. Rheum Dis Clin North Am. 2019 Nov;45(4):505–17. [PubMed: 31564293]