Psoriatic arthritis

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Understanding this condition

What psoriatic arthritis is

PsA is an immune-mediated inflammatory arthritis within the spondyloarthritis family, associated with cutaneous psoriasis. Musculoskeletal disease may precede, coincide with, or follow skin involvement. Pathology spans synovitis, enthesitis, and new bone formation. Provided as orientation; not sourced on this draft.

Signs and symptoms

Presentations include asymmetric oligoarthritis, polyarthritis (which may mimic RA), DIP-predominant disease, dactylitis, enthesitis (for example plantar fascia, Achilles), axial involvement, and nail dystrophy. Inflammatory back pain suggests axial PsA. Not sourced on this draft.

Who gets it, and why

PsA occurs in a minority of patients with psoriasis, with familial aggregation and HLA associations. Typical onset is mid-adulthood with roughly equal sex distribution. The proportion of psoriasis patients who develop PsA varies across studies; figures are intentionally not asserted here and are to be sourced.

How it is diagnosed

Diagnosis is clinical, integrating the musculoskeletal, skin, and nail examination with imaging (ultrasound, radiographs, MRI for axial or entheseal disease) and inflammatory markers. RF and anti-CCP are usually negative, aiding differentiation from RA. The CASPAR criteria support classification. Not sourced on this draft.

What to expect over time

With early, target-driven treatment a substantial proportion achieve low disease activity across domains and avoid significant structural damage. Poor prognostic markers (polyarticular disease, early erosions, high acute-phase response, dactylitis) inform therapy intensity. Outcome proportions to be sourced.

Living with and treating it

The goal of treatment

The target is the lowest possible level of disease activity across every active domain, assessed at intervals with therapy adjusted accordingly. Shared decision-making and dermatology co-management are central. GRAPPA 2021 states the ultimate goals of therapy as achieving the lowest possible level of disease activity in all domains of disease; optimising functional status, quality of life and wellbeing, and preventing structural damage to the greatest extent possible; and avoiding or minimising complications, both from untreated active disease and from therapy (Table 1; agreement 87.5 per cent from patient research partners, 96.3 per cent from clinicians). Note that GRAPPA does not fix a numeric target: it states that as definitions of remission and of low or minimal disease activity become accepted, these will be included in the goal. Assessment requires consideration of all disease domains, including peripheral arthritis, axial disease, enthesitis, dactylitis, skin psoriasis, psoriatic nail disease, uveitis and inflammatory bowel disease, examining the impact of disease on pain, function, quality of life and structural damage. Clinical assessment ideally includes patient-reported measures with a comprehensive history and physical examination, often supplemented by laboratory tests and imaging (for example X-ray, ultrasound or MRI), using the most widely accepted metrics validated for PsA wherever possible. Patients should be reviewed promptly, offered regular evaluation by appropriate specialists, and have treatment adjusted as needed to achieve the goals of therapy; early diagnosis and treatment is likely to be of benefit. Where a conventional synthetic DMARD is used first line for peripheral arthritis, GRAPPA advises regular assessment of clinical response every 12 to 24 weeks, with early escalation of therapy between 12 and 24 weeks as necessary. Separately, the ACR/NPF 2018 guideline recommends a treat-to-target strategy over not using one in active PsA, as a conditional recommendation on low-quality evidence (Table 5, PICO 44), and points to minimal disease activity (MDA) or the Disease Activity index for Psoriatic Arthritis (DAPSA) as the likely target, though another target may be chosen through patient and provider discussion. Neither guideline sets numeric cut-offs for those instruments, and none is asserted here.

Treatments that change the disease

Therapy is domain-directed: NSAIDs and local glucocorticoid for mild peripheral or entheseal disease; csDMARDs (for example methotrexate) for peripheral arthritis and skin; bDMARDs (TNF, IL-17, or IL-23 directed) and tsDMARDs (JAK inhibitors) for inadequate response or for enthesitis, axial, or significant skin disease, with agent choice matched to domain profile, skin severity, and comorbidity (for example IBD or uveitis). Systemic glucocorticoids are generally minimised. Class choices and caveats must be set from primary guidance; unsourced here.

Monitoring and follow-up

Monitoring combines multi-domain disease-activity assessment with drug-safety surveillance appropriate to the agent. GRAPPA 2021 frames treatment as an iterative process: assess activity in each domain, consider comorbidities, previous therapies and patient preference, then treat and periodically re-evaluate the treatment goals and modify therapy as required; comorbidities and associated conditions may themselves impact the choice of therapy and guide monitoring. For peripheral arthritis on a conventional synthetic DMARD, it advises assessing clinical response every 12 to 24 weeks with early escalation between 12 and 24 weeks as necessary. Before starting immunomodulatory therapy, GRAPPA advises screening for active hepatitis B and hepatitis C, seeking gastroenterology or hepatology input on antivirals for active HCV or active or past HBV; screening for HIV, with treatment decisions made with infectious diseases if positive; and screening for active or latent tuberculosis prior to initiation of therapy, since bDMARDs, particularly TNF inhibitors, can increase the risk of developing active tuberculosis. Herpes zoster risk appears higher with JAK inhibitors than with other immunomodulatory therapies: counsel patients and encourage vaccination before starting therapy where accessible. Where immunomodulatory therapy or previous phototherapy raises the risk of non-melanoma skin cancer, patients should be counselled and encouraged to undergo full skin assessment annually. Fatty liver disease is common and should be considered when monitoring liver function on medication and when selecting therapies that could affect the liver. Drug-safety laboratory intervals are agent-specific and are set out on each medication guide rather than restated here, so that one reviewed record drives both the disease guide and the medicine guide; for conventional synthetic DMARDs such as methotrexate the ACR schedule (defined for rheumatoid arthritis) is baseline complete blood count, transaminases and creatinine, then every 2 to 4 weeks for the first 3 months, every 8 to 12 weeks from 3 to 6 months, and every 12 weeks beyond 6 months, testing more often after a dose increase. On drug levels, GRAPPA records that therapeutic drug monitoring has been considered but the limited data published to date do not support its regular use in PsA.

Flares, and what to do

A flare is increased activity above the patient's controlled baseline, which may involve any domain. Management includes review of adherence and triggers, targeted symptomatic measures, and reassessment of the regimen for recurrent flares. Fever with a single hot joint warrants exclusion of septic arthritis. Not sourced on this draft.

Living well with PsA

Non-drug care complements systemic therapy: structured exercise and physiotherapy, weight management (associated with improved activity and treatment response), smoking cessation, skin care in partnership with dermatology, cardiovascular and metabolic risk management, vaccination per the immunosuppression schedule, and attention to mood and fatigue. Specific thresholds to be sourced.

Looking after the rest of you

Psoriasis and PsA are associated with several chronic conditions that influence treatment choice, response, quality of life and mortality. GRAPPA 2021 identifies the comorbidities of particular importance as cardiovascular disease, obesity, metabolic syndrome, liver disease (fatty liver disease in particular), mood disorders including depression and anxiety, chronic infections (hepatitis B, hepatitis C, HIV, tuberculosis and fungal infections), malignancy (for example skin cancer and lymphoma), osteoporosis, and fibromyalgia or central sensitisation. Cardiovascular risk is elevated compared with the age-matched and sex-matched general population: screen for cardiovascular risk factors and manage modifiable ones, which any of the clinicians caring for the patient can do (rheumatologist, dermatologist, cardiologist or primary care). Obesity is associated with reduced function, greater psoriasis severity and disease activity, and reduced response to therapy, so encourage a healthy weight. Screening for mood disorders should be part of the standard clinic review, with referral for diagnosis and psychological support as appropriate, since depression and anxiety are highly prevalent and are strong negative predictors of joint remission. Surveillance and treatment of osteoporosis should be the same as in the general population. Identifying and managing fibromyalgia or central sensitisation can improve quality of life and reduce treatment cycling. GRAPPA sets out a comorbidity-by-drug-class matrix (Table 4), for example caution with NSAIDs and JAK inhibitors where cardiovascular risk is elevated; caution with glucocorticoids and avoidance of TNF inhibitors in severe or advanced congestive heart failure (NYHA class III or IV); caution with JAK inhibitors where VTE risk is elevated; avoidance of methotrexate or leflunomide in fatty liver disease; and caution across TNF, IL-17, IL-12/23, IL-23, JAK and PDE4 inhibitors in active hepatitis B or C, HIV, tuberculosis, and a history of recent malignancy. For related conditions, methods of screening for IBD in PsA have not been evaluated in randomised trials, but criteria that might prompt referral for evaluation of possible IBD include chronic diarrhoea of 3 months or more, nocturnal bowel symptoms causing waking from sleep, non-haemorrhoidal rectal bleeding, chronic abdominal pain, perianal fistula or abscess, and weight loss. GRAPPA is explicit that it does not give recommendations on the treatment of comorbidities, only advice on their general management, since there is no clear evidence that these comorbidities are treated differently in PsA than in the general population, and this is typically beyond the scope of the treating rheumatologist or dermatologist. Beyond the annual skin assessment noted above, no screening interval is set by the guideline, and none is asserted here.

What to expect at your rheumatology visit

The initial encounter establishes the diagnosis and active domains, assesses skin and comorbidity, initiates therapy, and sets the treat-to-target plan with the patient, ideally coordinated with dermatology. Structured follow-up is more frequent during escalation. Orientation content; not sourced.

Verified against Taylor W, et al. Classification criteria for psoriatic arthritis (Arthritis Rheum 2006;54(8):2665-2673, Table 6). Reported specificity 98.7 percent and sensitivity 91.4 percent.

Treatment ladder

1. 1

   First step (mild or single-domain disease)

   For mild peripheral or entheseal disease, NSAIDs and local glucocorticoid injections are conditionally recommended (entheseal injection only with extreme caution), with prompt escalation if inadequate (GRAPPA 2021).

   Verified against GRAPPA 2021 (Table 3, peripheral and enthesitis domains).

2. 2

   For ongoing joint disease

   For persistent peripheral arthritis, a csDMARD, methotrexate commonly used and also helpful for skin (csDMARDs strongly recommended for DMARD-naive peripheral arthritis; GRAPPA 2021). csDMARDs are not recommended for axial disease and are limited for enthesitis.

   Verified against GRAPPA 2021 (Table 3): csDMARDs strong for peripheral, not recommended for axial.

3. 3

   Advanced, targeted treatment

   TNF, IL-17, IL-23, and IL-12/23 inhibitors, JAK inhibitors, and PDE4 inhibitors are strongly recommended across peripheral, enthesitis, dactylitis, skin, and nail domains; for axial disease, TNF or IL-17 inhibitors or a JAK inhibitor are recommended. Choice is matched to the active domains, skin severity, and comorbidity, for example avoiding IL-17 inhibitors in inflammatory bowel disease.

   Verified against GRAPPA 2021 (Table 3 by domain; Table 4 comorbidities, including IL-17i and IBD).

4. 4

   When the disease is well controlled

   Once treatment goals are achieved, tapering may be considered with the patient's understanding that disease may reactivate and the target may not be regained (GRAPPA 2021 position statement).

   Verified against GRAPPA 2021 (Table 2, tapering position statements).

Recommendations by domain (GRAPPA 2021, Table 3)

GRAPPA sets recommendations per domain rather than as a single ladder, because most people have disease in more than one domain and therapy should address as many active domains as possible. The table shows the recommendation for each drug class within each domain. It does not rank drugs within a strength: order does not imply preference, and GRAPPA states the table gives no hierarchy within the strong or conditional recommendations.^[1]

Abbreviations: bDMARD, biologic DMARD; csDMARD, conventional synthetic DMARD (MTX, SSZ, LEF, CsA unless otherwise specified); CsA, ciclosporin; CTLA4-Ig, abatacept; ETN, etanercept; GC, glucocorticoid; IA, intra-articular; IBD, inflammatory bowel disease; IL-12/23i, IL-12 and IL-23 inhibitor; IL-17i, IL-17 inhibitor; IL-23i, IL-23 inhibitor; JAKi, Janus kinase inhibitor; LEF, leflunomide; MTX, methotrexate; PDE4i, phosphodiesterase 4 inhibitor (apremilast); SIJ, sacroiliac joint; SSZ, sulfasalazine; TNFi, TNF inhibitor. 'No recommendation' means insufficient or conflicting evidence, not evidence of no effect. The related-conditions rows (IBD, uveitis) are a resource for approaching active disease in those domains in someone with PsA; GRAPPA states they are not primary recommendations for treating those conditions, and their management should involve the appropriate specialist. GRAPPA prints 'cdDMARDs' in the plaque psoriasis row; read as csDMARDs, per the table's own key.

Guideline recommendations

Key points

Medication guides

Plain-language guides to the medicines used for this condition. Each has a patient and a clinician view.

• Methotrexate
• NSAIDs
• Glucocorticoids
• TNF inhibitors
• IL-17 inhibitors
• Ustekinumab
• JAK inhibitors

References

1. Coates LC, et al. Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA): updated treatment recommendations for psoriatic arthritis 2021. Nat Rev Rheumatol. 2022;18(8):465-479. https://doi.org/10.1038/s41584-022-00798-0
2. Singh JA, et al. 2018 American College of Rheumatology/National Psoriasis Foundation Guideline for the Treatment of Psoriatic Arthritis. Arthritis Rheumatol. 2019;71(1):5-32. https://doi.org/10.1002/art.40726
3. Taylor W, et al. Classification criteria for psoriatic arthritis: development of new criteria from a large international study. Arthritis Rheum. 2006;54(8):2665-2673. https://doi.org/10.1002/art.21972
4. Coates LC, Corp N, van der Windt DA, O'Sullivan D, Soriano ER, Kavanaugh A. GRAPPA Treatment Recommendations: 2021 Update. J Rheumatol. 2022. doi:10.3899/jrheum.211331. Meeting report; Table 1 is an unpopulated skeleton. https://doi.org/10.3899/jrheum.211331