Psoriatic arthritis is a seronegative spondyloarthropathy and chronic inflammatory arthritis that occurs in people with psoriasis of the skin or nails. The arthritis is often asymmetric, and some forms involve the distal interphalangeal joints. Diagnosis is clinical. Treatment involves disease-modifying antirheumatic drugs (DMARDs) and biologic agents.
Psoriatic arthritis develops in about 30% of patients with psoriasis. Prevalence is increased in patients with AIDS. Risk is increased in patients with human leukocyte antigen B27 (HLA-B27) or some other specific alleles (HLA-Cw6, HLA-B38, HLA-B39, HLA-DR) in family members. Etiology and pathophysiology of psoriatic arthritis are unknown.
Symptoms and Signs of Psoriatic Arthritis
Psoriasis of the skin or nails may precede or follow joint involvement. Severity of the joint and skin disease is often discordant. Also, skin lesions may be hidden in the scalp, ears, gluteal folds, or umbilicus and go unrecognized by the patient.
Peripheral psoriatic arthritis may involve small, medium, and large joints with a high tendency to affect distal interphalangeal joints of fingers and toes. It may manifest in different patterns such as asymmetric oligoarthritis, symmetric polyarthritis (which can be confused with rheumatoid arthritis), and arthritis mutilans that is characterized by rapid destructive arthritis with telescoping of the digits.
Joint and skin symptoms may lessen or worsen simultaneously. Inflammation of the flexor tendons of fingers, toes, or both may lead to sausage-shaped deformities (dactylitis), which are not present in patients with rheumatoid arthritis. Rheumatoid nodules are absent. Arthritic remissions tend to be more frequent, rapid, and complete than in rheumatoid arthritis, but progression to chronic arthritis and crippling may occur.
Enthesopathy (inflammation at tendinous insertion into bone—eg, Achilles tendinitis, patellar tendinitis, elbow epicondyles, spinous processes of the vertebrae) can develop and cause pain and swelling.
Axial involvement may be present, especially in male patients with positive HLA-B27, and usually manifests as asymmetric involvement of the sacroiliac joints.
Image courtesy of Kinanah Yaseen, MD.
© Springer Science+Business Media
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
SCIENCE PHOTO LIBRARY
Image courtesy of Kinanah Yaseen, MD.
© Springer Science+Business Media
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
SCIENCE PHOTO LIBRARY
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 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.
Treatment of Psoriatic Arthritis
Treatment of psoriatic arthritis is directed at controlling skin lesions and at reducing joint inflammation. A treat-to-target approach to achieve full disease remission or minimal disease activity has been suggested and can be assessed at each visit by using the disease activity index for psoriatic arthritis (DAPSA) or minimal disease activity (MDA) scores (1, 2).
Drug therapy has been similar to that for rheumatoid arthritis, particularly using the DMARDnonsteroidal anti-inflammatory drugsBiologic agents). TNF-alpha antagonists have been particularly effective.
is usually given as enteric-coated tablets. Benefit should occur within 3 months. Enteric coating or dose reduction may increase tolerability. Because neutropenia may occur early, complete blood count (CBC) should be obtained after 1 to 2 weeks and then about every 12 weeks during therapy. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) should be obtained at about 6-month intervals and whenever the dose is increased. Response has been inconsistent.
is a phosphodiesterase-4 inhibitor that is effective for psoriasis and psoriatic arthritis. The initial dosage is 10 mg orally once/day, titrated to the maintenance dose of 30 mg orally twice a day as tolerated. Adverse effects include diarrhea, nausea, headache, depression, and weight loss. Skin is often more responsive to this medication than the joints.
Tumor necrosis factor (TNF)-alpha antagonistsrheumatoid arthritis treatment for more details about TNF inhibitors). TNF inhibitors occasionally paradoxically trigger psoriaform reactions including plaque, palmoplantar pustular, and guttate psoriasis.
is an interleukin (IL)-12 and IL-23 antagonist. The dosage is 45 mg subcutaneously at weeks 0 and 4 (loading dosages) followed by 45 mg every 12 weeks thereafter. The dosage is 90 mg subcutaneously if the patient weighs > 100 kg. Adverse effects are similar to those of the other biologic agents.
is an anti-IL-23-specific monoclonal antibody that is effective in treating moderate to severe psoriasis and has shown to be effective in treating psoriatic arthritis as well. It is given by subcutaneous injections at a recommended dose of 100 mg at weeks 0 and 4 and every 8 weeks thereafter.
Candida, diarrhea, herpes zoster, and worsening inflammatory bowel disease.
Rheumatoid Arthritis: Treatment for more details about major cardiovascular adverse events and malignancies with JAK inhibitors (3).
Treatment references
1. Schoels MM, Aletaha D, Smolen JS: Defining remission and treatment success using the DAPSA score: response to letter by Helliwell and Coates. Ann Rheum Dis 74(12):e67, 2015. doi:10.1136/annrheumdis-2015-208521
2. Coates LC, Helliwell PS: Validation of minimal disease activity criteria for psoriatic arthritis using interventional trial data. Arthritis Care Res (Hoboken) 62(7):965-969, 2010. doi:10.1002/acr.20155
3. Ytterberg SR, Bhatt DL, Mikuls TR, et al: Cardiovascular and cancer risk with tofacitinib in rheumatoid arthritis. N Engl J Med 386(4):316-326, 2022. doi:10.1056/NEJMoa2109927
Key Points
Psoriatic arthritis is chronic inflammatory spondyloarthropathy that occurs in patients with psoriasis; however, psoriasis may be mild or overlooked or may have not yet developed.
Arthritis is commonly asymmetric, involves large and small joints (including axial joints), and typically affects the finger and toe distal interphalangeal (DIP) joints more than others.
Diagnose based on clinical findings.
Treat with disease-modifying antirheumatic drugs (DMARDs) and biologic agents.
