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. Disparity between the severity of the skin and joint involvement is common. Diagnosis is clinical. Treatment involves disease-modifying antirheumatic drugs (DMARDs).
Psoriatic arthritis develops in approximately 20% of patients with psoriasis (1). Prevalence is increased in patients with HIV infection. 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 (2). Etiology and pathophysiology of psoriatic arthritis are unknown.
General references
1. Alinaghi F, Calov M, Kristensen LE, et al: Prevalence of psoriatic arthritis in patients with psoriasis: a systematic review and meta-analysis of observational and clinical studies. J Am Acad Dermatol 80(1):251-265.e19, 2019. doi:10.1016/j.jaad.2018.06.027
2. Gladman DD, Anhorn KA, Schachter RK, Mervart H: HLA antigens in psoriatic arthritis. J Rheumatol. 1986;13(3):586-592.
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. 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 similar manifestations. Radiographic 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
For axial disease, nonsteroidal TNF inhibitors, IL-17 inhibitors, and Janus kinase (JAK) inhibitors
Treatment of psoriatic arthritis is directed at controlling skin lesions and reducing joint inflammation. The approach to treatment selection is guided by the disease impact on different domains (eg, peripheral arthritis, axial arthritis, dactylitis, enthesitis, skin disease). (See 2018 American College of Rheumatology/National Psoriasis Foundation Guideline for the Treatment of Psoriatic Arthritis, EULAR recommendations for the management of psoriatic arthritis with pharmacological therapies: 2019 update, and Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA): updated treatment recommendations for psoriatic arthritis 2021.)
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).
Therapeutic options for axial involvement include TNF inhibitors, IL-17 inhibitors, and JAK inhibitors.
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. 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) inhibitors3). TNF inhibitors occasionally paradoxically trigger psoriaform reactions including plaque, palmoplantar pustular, and guttate psoriasis.
Candida, diarrhea, herpes zoster, and worsening inflammatory bowel disease.
Ixekizumab increases the risk of upper respiratory infections and fungal infections and has also been associated with worsening symptoms of inflammatory bowel disease.
is an interleukin IL-12 and IL-23 antagonist. Adverse effects include risk of infection and noninfectious pneumonia.
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.
Rheumatoid Arthritis: Treatment for more details about major cardiovascular adverse events and malignancies with JAK inhibitors (4).
Abatacept may be given as an IV infusion or as a subcutaneous injection. Adverse effects include pulmonary toxicity, susceptibility to infection, headache, upper respiratory infection, sore throat, and nausea.
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. Goulabchand R, Mouterde G, Barnetche T, et al: Effect of tumour necrosis factor blockers on radiographic progression of psoriatic arthritis: a systematic review and meta-analysis of randomised controlled trials. Ann Rheum Dis. 2014;73(2):414-419. doi:10.1136/annrheumdis-2012-202641
4. 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) based on the predominant domains involved (eg, peripheral and/or axial arthritis).
