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Psoriatic arthritis (PsA)

Psoriatic arthritis is a long-term inflammatory arthritis that occurs in people affected by the autoimmune disease psoriasis.

Both psoriatic arthritis and rheumatoid arthritis are autoimmune diseases in which the immune system attacks the joints, causing inflammation and pain. Indeed, it is easy to confuse the two conditions because of similar symptoms. | Alamy; Getty Images

Psoriatic arthritis is a long-term inflammatory arthritis that occurs in people affected by the autoimmune disease psoriasis.

  • Type of seronegative spondyloarthropathy

Etiology

The etiology and pathogenesis of psoriatic arthritis are not fully understood but involves a complex interaction between genetic and environmental factors resulting in immune-mediated inflammation involving the skin and joints and may involve other organs.

Transition phases from psoriasis to early PsA | Zabotti, A., Tinazzi, I., Aydin, S. Z., & McGonagle, D. (2020). From Psoriasis to Psoriatic Arthritis: Insights from Imaging on the Transition to Psoriatic Arthritis and Implications for Arthritis Prevention. Current rheumatology reports, 22(6), 24. https://doi.org/10.1007/s11926-020-00891-x

Genetic factors:

Approximately 33 to 50% of psoriatic arthritis patients have at least one first degree relative who also has psoriasis or psoriatic arthritis. The genetic associations with psoriatic arthritis and psoriasis are not identical so that some genes associated with psoriatic arthritis are not associated with psoriasis, and the same is true for psoriasis. Also, certain genes are associated with specific phenotypes of psoriatic arthritis.
  • HLA genes: Involved in antigen presentation and immune recognition
    • Symmetric polyarthritis: HLA-DR4
    • Axial involvement: HLA-B27
    • Non-symmetric polyarthritis: HLA-B38 & HLA-B39
    • Psoriasis susceptibility region 1 (PSORS1): HLA-B57:01 and HLA-C06:02
      • Psoriasis has a stronger association than psoriatic arthritis with this region
  • Non-HLA genes: Involved in immune activation and inflammation including intracellular signaling, cytokine expression, and signaling, and T cell effector function.
    • IL-23R
    • IL-12B: Associated with psoriasis but not psoriatic arthritis.

Environmental factors:

  • Streptococcal infection and recent antibiotic exposure
  • Koebner phenomenon: Skin trauma is known to induce flares of psoriatic skin lesions
  • Internal/deep Koebner phenomenon: Joint trauma may induce a flare of arthritis

Protective factors:

  • Tobacco: Trigger for rheumatoid arthritis in patients with certain HLA-DR genes, appears to be protective for the development of psoriatic arthritis

Presentation

The clinical manifestations are varied and can change over time, evolving from one articular pattern to another.

Articular/periarticular manifestations:

  • Peripheral arthritis: Oligoarticular vs. polyarticular pattern
  • Enthesitis: Inflammation around the insertion of ligaments, tendons, or joint capsules
  • Dactylitis: Swelling of entire digit/finger/toe “sausage digit”
  • Tenosynovitis
  • Axial disease: Involving sacroiliac joints, usually asymmetric and spondylitis with discontinuous involvement with bulky non-marginal syndesmophytes
Peripheral hand joint involvement along with psoriatic skin lesion and nail changes. | Dhir V, Aggarwal A. Psoriatic arthritis: a critical review. Clin Rev Allergy Immunol. 2013;44:141–148.

Extra-articular manifestations:

  • Psoriatic skin disease: Usually presents before the onset of arthritis but can occur simultaneously and even before the onset of joint disease. The severity of skin disease does not correlate well with the severity of the articular disease.
  • Psoriatic nail disease: Onycholysis, pitting, and splinter hemorrhages. The severity of nail disease correlates with the severity of both skin and joint disease. It is present in 80 to 90% of patients with psoriatic arthritis and is associated with DIP joint involvement.
  • Psoriatic Ocular disease: Uveitis but unlike that associated with ankylosing spondylitis, it is often chronic, bilateral, and often involves posterior elements.
Onychody-strophy due to psoriasis: findings include nail yellowing, onycholysis, and subungual hyperkeratosis | Kimmel, G. W., & Lebwohl, M. (2018). Psoriasis: Overview and Diagnosis. Evidence-Based Psoriasis: Diagnosis and Treatment, 1–16. https://doi.org/10.1007/978-3-319-90107-7_1

Diagnosis

Serology:

  • Acute phase reactants: Elevated as in most inflammatory diseases
    • ESR (erythrocyte sedimentation rate)
    • CRP (C-reactive protein)
  • Seronegative arthropathy findings:
    • RF and anti-CCP antibodies classically absent

CASPAR criteria (Classification of Psoriatic Arthritis):

Most accepted classification criteria for psoriatic arthritis; in use since 2006
Classification Criteria for Psoriatic Arthritis (CASPAR) | Remaining On This. (2021) Case Report: A Psoriatic Arthritis Patient with Dactylitis & Enthesitis – Page 2 of 8 – The Rheumatologist. Retrieved October 17, 2021, from https://www.the-rheumatologist.org/article/case-report-a-psoriatic-arthritis-patient-with-dactylitis-enthesitis/2/

Radiographic findings:

Findings are driven by bone destruction and pathologic new bone formation often in the same digit or even the same joint, which is a characteristic feature of psoriatic arthritis; bone destruction with bone production. Despite treatment with DMARDs (disease-modifying anti-rheumatic drugs), psoriatic arthritis results in radiographic damage in about 47% of patients during the first two years of the disease.

Peripheral arthritis findings:

Characteristic pattern of erosive changes, gross joint destruction, joint space narrowing is seen.
  • Erosive changes (including MCP, PIP, DIP joints, and wrists)
  • New bone formation
  • Bony ankylosis
  • Joint osteolysis
  • “Pencil-in-cup” deformity
Psoriatic Arthritis: Arthritis Mutilans in patient with Psoriatic Arthrits, showing destruction of both hand joints. A “pencil in cup” change of the metacarpophalangeal joints is charcterisitic. Contributed by Pol J Radiol. 2013 Jan-Mar; 78(1): 7–17. (Open Access)

Entheseal involvement:

Characteristic in all spondyloarthropathies
  • Erosions and new bone formation
a–b Dorsal scan of the Achilles tendon. a–b Longitudinal view. Active enthesitis with loss of the tightly packed echogenic lines (white asterisks) and concomitant PD signal at bone insertion in a psoriatic arthralgia patient. c Lateral scan on the elbow. Active enthesitis of the common extensor tendon enthesis in an early psoriatic arthritis. d Plantar fascia. Thickening of the plantar fascia in a psoriasis patient. | AT, Achilles tendon; C calcaneus; CET common extensor tendon enthesis; PF plantar fascia | Zabotti, A., Tinazzi, I., Aydin, S. Z., & McGonagle, D. (2020). From Psoriasis to Psoriatic Arthritis: Insights from Imaging on the Transition to Psoriatic Arthritis and Implications for Arthritis Prevention. Current rheumatology reports, 22(6), 24. https://doi.org/10.1007/s11926-020-00891-x

Axial features:

The features which differentiate psoriatic arthritis from ankylosing spondylitis are the asymmetric and often unilateral presentation of sacroiliitis. Syndesomophytes in psoriatic arthritis are often bulkier, asymmetric, and discontinuous skipping vertebral levels.
  • Sacroiliitis and spondylitis
  • Syndesmophytes (ossification of the annulus fibrosis)
Inflammatory changes in sacroiliac joints. Marked asymmetry with more prominent erosions on the left side. | Sankowski, A. J., Lebkowska, U. M., Cwikła, J., Walecka, I., & Walecki, J. (2013). Psoriatic arthritis. Polish journal of radiology, 78(1), 7–17. https://doi.org/10.12659/PJR.883763

Differential diagnosis:

  • Rheumatoid arthritis
  • Osteoarthritis
  • Reactive arthritis
  • Gouty arthritis
  • Systemic lupus erythematosus
  • Inflammatory bowel disease-associated arthritis

Management

Treatment options:

  • Non-pharmacologic therapies: Physical therapy & occupational therapy, smoking cessation, weight loss, exercise
  • Symptomatic management: NSAIDs, glucocorticoids
  • Oral small molecules (OSMs): Methotrexate, sulfasalazine, cyclosporine, leflunomide, apremilast
  • Tumor necrosis factor inhibitor (TNFi) biologics: Etanercept, infliximab, adalimumab, golimumab, certolizumab pegol
  • IL-12/23 inhibitor biologic: Ustekinumab
  • IL-17 inhibitor biologics: Secukinumab, ixekizumab, brodalumab
  • CTLA4-immunoglobulin: Abatacept
  • JAK inhibitor: Tofacitinib

Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) recommendations:

Group for Research and Assessment of Psoriasis and Psoriatic Arthritis treatment schema for active psoriatic arthritis (PsA). Light text identifies conditional recommendations for drugs that do not currently have regulatory approvals or for which recommendations are based on abstract data only. | NSAIDs = nonsteroidal antiinflammatory drugs; IA = intraarticular; DMARDs = disease-modifying antirheumatic drugs; MTX = methotrexate; SSZ = sulfasalazine; LEF = leflunomide; TNFi = tumor necrosis factor inhibitor; PDE-4i = phosphodiesterase 4 inhibitor (apremilast); IL-12/23i = interleukin-12/23 inhibitor; SpA = spondyloarthritis; CS = corticosteroid; vit = vitamin; phototx = phototherapy; CSA = cyclosporin A. | Coates, L.C., Kavanaugh, A., Mease, P.J., Soriano, E.R., Laura Acosta-Felquer, M., Armstrong, A.W., Bautista-Molano, W., Boehncke, W.-H., Campbell, W., Cauli, A., Espinoza, L.R., FitzGerald, O., Gladman, D.D., Gottlieb, A., Helliwell, P.S., Husni, M.E., Love, T.J., Lubrano, E., McHugh, N., Nash, P., Ogdie, A., Orbai, A.-M., Parkinson, A., O’Sullivan, D., Rosen, C.F., Schwartzman, S., Siegel, E.L., Toloza, S., Tuong, W. and Ritchlin, C.T. (2016), Group for Research and Assessment of Psoriasis and Psoriatic Arthritis 2015 Treatment Recommendations for Psoriatic Arthritis. Arthritis & Rheumatology, 68: 1060-1071. https://doi.org/10.1002/art.39573

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