Introduction

• Psoriatic arthritis (PsA) affects up to 1%^1,2 of the population. The proportion of patients with skin psoriasis who develop PsA is uncertain, with estimates ranging from 6% to 42%,^1,3,4 usually within 5 to 10 years of cutaneous disease onset¹
• Patients with psoriasis or PsA, or both, generally have reduced health-related quality of life, productivity, and functionality¹
• Approximately two-thirds of patients with PsA develop joint damage;⁵ joint erosions develop within 2 years of PsA symptom onset in approximately 50% of patients⁴
• The presence of PsA and psoriasis adds approximately USD 23 000/year (approximately EUR 20 000) to the total medical costs versus patients without PsA and psoriasis⁶

Differences between PsA and rheumatoid arthritis

Despite apparent similarities between PsA and rheumatoid arthritis, there are important differences between them.⁷

	Psoriatic arthritis	Rheumatoid arthritis
Clinical/anatomical	Distal interphalangeal joint and axial arthritis Often asymmetrical Enthesitis common	Metacarpophalangeal and wrist joints Predominantly symmetrical
Genetic	HLA Cw6 and B27 IL-23 receptor	HLA DRB1
Pathogenesis	Absence of circulating autoantibodies Distinct vascular pathology T-lymphocyte predominance Early expression of vascular growth factors	Circulating autoantibodies RF/ACPA T-lymphocyte and B-lymphocyte infiltrate Late expression of vascular growth factors
Response to therapy	DMARDs, e.g. MTX Anti-TNF antibodies Inhibitors of T-cell activation Anti-IL-12/23 Anti-IL-17a	DMARDs, e.g. MTX Anti-TNFs Inhibitors of T-cell activation Anti-CD20 Anti-IL-6R

ACPA, anti-citrullinated protein antibody; DMARD, disease-modifying anti-rheumatic drug; HLA, human leukocyte antigen; IL, interleukin; MTX, methotrexate; RF, rheumatoid factor; TNF, tumor necrosis factor.

Adapted from Veale and Fearon, 2015.⁷

Burden of PsA

PsA: Under-diagnosis and under-treatment

• PsA is believed to be underdiagnosed;⁸ if untreated, it can lead to severe disability and comorbidities⁹
• An international survey of 712 patients with PsA found that more than half of patients (59%) reported that they were receiving no treatment or receiving topical therapy but were not receiving any systemic medication for their joint disease¹⁰

Multinational Assessment of Psoriasis and Psoriatic Arthritis (MAPP) survey: Affected joint count and self-perceived severity¹⁰

A total of 712 patients with PsA were included. ^*Including only patients with PsA who reported joint pain (n=628).

Adapted from Kavanaugh et al, 2016.¹⁰

Impact

Many patients with PsA experience a considerable impairment in physical function. The impact of impaired physical function progressively increases with the number of affected joints or symptoms resembling enthesitis or dactylitis, as assessed by Health Assessment Questionnaire (HAQ-8 or modified HAQ). PsA also severely impacts patients’ work productivity.¹⁰ 

MAPP survey: Impact of PsA on physical function¹⁰

The proportions of patients who responded ‘with much difficulty’ or ‘unable to do’ are shown.

Adapted from Kavanaugh et al, 2016.¹⁰ 

MAPP survey: Impact of PsA on work productivity¹⁰

Shown for ‘Missed work in past 12 months’ is the proportion of patients who responded with ‘yes’; all other responses represent the proportion of patients reporting ‘a lot’ or ‘some’ impact of PsA.

Adapted from Kavanaugh et al, 2016.¹⁰ 

Treatment

Treatment options in PsA

Treatment	Comments
NSAIDs	Still widely used for PsA treatment, especially in very mild disease Can relieve musculoskeletal symptoms, but have no efficacy on psoriasis skin lesions Lower toxicity compared with DMARDs
Steroids	Local injections of steroids can be used as adjunctive therapy for peripheral arthritis and enthesitis Systemic steroids, particularly high doses, should be used with caution because they have been associated with psoriasis flares
Conventional DMARDs	Patients with active disease despite NSAID therapy should receive DMARDs DMARDs are ineffective in axial disease, and there is little evidence that they are efficacious for treatment of enthesitis MTX MTX is recommended in guidelines as the first choice DMARD, either as monotherapy or in combination Sulfasalazine May improve peripheral arthritis and functional outcomes No evidence that it can inhibit progression of joint damage Leflunomide May improve joint and skin symptoms in PsA The combination of leflunomide and MTX is associated with elevated liver function test results and so should be monitored carefully Cyclosporine and tacrolimus May be effective for the treatment of peripheral arthritis, axial involvement, and skin lesions Adverse events potentially associated with cyclosporine include renal toxicity and hypertension, and requiring monitoring during treatment
Biologics	Anti-TNFs Can improve signs and symptoms of inflammation in both peripheral and axial joints as well as in peri-articular tissues such as entheses Can also improve functional status, quality of life, and skin and nail manifestations of PsA Can slow the progression of damage in peripheral joints Options include etanercept, infliximab, adalimumab, golimumab, and certolizumab pegol IL-12/23 inhibitor (ustekinumab) Evidence of efficacy in PsA in terms of ACR20 and ACR50 responses, and evidence of slowed radiographic progression IL-17 inhibitor (secukinumab) Evidence of improvement of joint symptoms and radiographic progression
Small molecular-weight inhibitors	Phosphodiesterase inhibitor (apremilast) Downregulates the inflammatory response Has been shown to be effective in PsA, improving signs, symptoms, and physical function Janus kinase inhibitor (tofacitinib) Inhibits cytokine signaling (including IL-2, IL-12, IL-6, and many others)

ACR20/50, 20/50% improvement in American College of Rheumatology criteria; DMARD, disease-modifying anti-rheumatic drug; IL, interleukin; MTX, methotrexate; NSAID, non-steroidal anti-inflammatory drug; TNF, tumor necrosis factor.

Adapted from Kang and Kavanaugh, 2015.¹¹

Guidelines

The Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) guidelines

The GRAPPA guidelines place equal emphasis on the dermatological and rheumatological aspects of PsA.

DMARD, disease-modifying anti-rheumatic drug; IA, intra-articular; IL, interleukin; NSAID, non-steroidal anti-inflammatory drug; PDE, phosphodiesterase; TNF, tumor necrosis factor.

Text in italics indicates conditional recommendations for drugs that do not currently have regulatory approvals or for which recommendations are based on abstract data only. 

Adapted from Coates et al, 2016.¹²

EULAR guidelines

Unlike GRAPPA, the EULAR guidelines put the primary emphasis on the musculoskeletal aspects of the disease.¹³

EULAR treatment guidelines¹³

CsA, ciclosporin A; (b-/cs-) DMARD, (biologic/conventional synthetic) disease-modifying anti-rheumatic drug; IL, interleukin; LEF, leflunomide; MTX, methotrexate; NSAID, non-steroidal anti-inflammatory drug; SSZ, sulphasalazine; TNF, tumor necrosis factor. 

Adapted from Gossec et al, 2016.¹³

Support

Additional information

You can find additional information about PsA by following these links:

NHS Choices:
http://www.nhs.uk/conditions/psoriatic-arthritis/Pages/Introduction.aspx

National Psoriasis Association:
https://www.psoriasis.org/psoriatic-arthritis

Psoriasis and Psoriatic Arthritis Alliance:
http://www.papaa.org/resources/about-psoriasis