Psoriatic arthritis

Synonyms: psoriatic arthropathy, arthropathia psoriatica, arthritis mutilans, seronegative arthritis associated with psoriasis

See also the separate Psoriasis of Hands and Feet (including Palmoplantar Pustulosis), Chronic Plaque Psoriasis, Erythrodermic Psoriasis and PUVA articles.

What is psoriatic arthritis?

Psoriatic arthritis is an inflammatory arthritis affecting the joints and connective tissue and is associated with psoriasis of the skin or nails. Occasionally psoriatic arthritis may occur in the absence of skin disease, or there may only be an insignificant rash which may not be noticed.

The National Institute for Health and Care Excellence (NICE) has defined active psoriatic arthritis as having 3 or more tender joints and 3 or more swollen joints in adults.¹

Psoriatic arthritis may involve not only the joints in the sense of arthritis but also the tendons surrounding the joints, leading to swelling of whole digits (dactylitis), or it may lead to inflammation of the entheses (enthesitis).²

Psoriatic arthritis is a progressive disorder ranging from mild synovitis to severe progressive erosive arthropathy. 40-60% of patients with psoriatic arthritis develop erosive and deforming joint complications.³

How common is psoriatic arthritis? (Epidemiology)⁴

The diverse clinical manifestations of this condition have impaired meaningful research on epidemiology. The diagnosis can easily be missed or overlooked.

• Psoriatic arthritis is a chronic seronegative inflammatory arthritis affecting 20-30% of people with psoriasis.⁵

• There is not a strong correlation between the severity of psoriasis and the development of arthritis.

• The prevalence of psoriasis in the general population is estimated at 2-4%.⁶

• Psoriatic arthropathy is more common in the western white population than in other races.

• Men are more commonly affected by the spondylitic subtype, with higher incidence of the 'rheumatoid' pattern of disease among women.

• It is most common in middle age (35-55) but may be seen in patients of any age.

Risk factors⁷

The possible risk factors for psoriatic arthritis include:

• Psoriatic nail disease.

• Family history of psoriatic arthritis.

• HLA-B27.

• Obesity.

• Smoking.

• Severe psoriasis.

• Psoriasis location: scalp lesions, intergluteal/perianal lesions.

Symptoms of psoriatic arthritis (presentation)⁵

Psoriatic arthritis has variable clinical presentations, with diverse articular and dermatological features and varied disease courses and outcomes. It is generally under-diagnosed.³

The characteristics of psoriatic arthritis include joint stiffness, pain and swelling, and tenderness of the joints and surrounding ligaments and tendons. Symptoms can range from mild to very severe. The arthritis tends to be relapsing and remitting. Psoriatic arthritis may present with:

• Inflammatory pain or peripheral joint swelling especially affecting the knees, ankles, hands, and feet; or dactylitis (swelling and tenderness of an entire digit).

• Inflammatory or night-time pain in the axial skeleton and at tendon insertions (enthesitis), especially affecting the Achilles tendon and/or plantar fascia.

• Psoriatic nail disease in up to 90% of cases.

• Enthesopathy affecting the Achilles tendon and plantar fascia is frequently seen. Tenosynovitis tends to affect the flexor rather than extensor tendons (both commonly affected in rheumatoid arthritis).

• Ocular involvement may be seen with conjunctivitis (20-30% of cases) and anterior uveitis (5% or so). Sacroiliitis and HLA-B27 positivity are commonly associated with ocular disease.

• Rarely aortitis, similar to that seen in ankylosing spondylitis or reactive arthritis, and secondary amyloidosis are features of the disease.

Skin psoriasis usually develops before joint involvement in the majority of cases, with a typical time lag of 5-10 years. However about 20% of people with psoriatic arthritis do not develop skin psoriasis.

40% of people with psoriatic arthritis fulfil the diagnosis for metabolic syndrome.⁸

An annual assessment for psoriatic arthritis should be offered to people with any type of psoriasis. Assessment is especially important within the first ten years of onset of psoriasis (psoriatic arthritis usually develops within ten years of a diagnosis of psoriasis).⁴

A validated tool to assess adults for psoriatic arthritis should be used in primary care and specialist settings - eg, the Psoriasis Epidemiological Screening Tool (PEST). However, PEST does not detect axial arthritis or inflammatory back pain.^{4 9}

Patterns of presentation

• Symmetrical polyarthritis ('rheumatoid' pattern). This is more common in women. Wrists, hands, feet and ankles are usually affected. Distal interphalangeal (DIP) joints are involved rather than metacarpophalangeal (MCP) joints, helping to distinguish it from rheumatoid arthritis, along with absence of skin nodules and a negative rheumatoid factor (RF) test.

• Asymmetric oligoarticular/pauciarticular arthritis. Hands and feet are affected initially with enthesopathy causing dactylitis ('sausage fingers'). Usually up to five joints are involved.

• Lone DIP disease. The nail and paronychial tissues can also be involved, along with the terminal phalanx, looking like an infection or traumatic 'hammer blow' appearance. This is usually seen in men.

• Arthritis mutilans. This is a relatively rare variation of DIP disease. Resorption of the terminal phalanx, giving a 'telescopic digit' appearance. It gives the classical 'pencil in cup' radiographic appearance. 'Opera-glass hand' (flexion deformity of the DIP joints), seen mainly in men with early-onset arthritis.

• Spondylitic pattern ± sacroiliitis. This is more common in men. There is morning stiffness and limitation of back movement. There may not be much in the way of symptoms and it may be noted radiologically. Unlike ankylosing spondylitis, the vertebrae are usually affected asymmetrically and there are sometimes bizarre radiological appearances such as syndesmophytes, paravertebral ossification and fusion of vertebral bodies with calcified intervertebral discs. The atlanto-axial joint may be involved, with destruction of odontoid peg and danger of subluxation.

• Juvenile onset. This accounts for up to a fifth of childhood arthritis and usually starts as a monoarthritis, but DIP pattern may be seen. Tenosynovitis affects up to a third and nail changes are present in about two thirds. Epiphyseal involvement can affect growth. Sacroiliitis may occur. Simultaneous onset of rash and arthritis is more common than in adults. See also the separate Juvenile Idiopathic Arthritis article.

Differential diagnosis

Features that distinguish psoriatic arthritis from other forms of inflammatory joint disease include the pattern of joint involvement (eg, DIP joint involvement), the swelling of an entire digit (dactylitis), the presence of enthesitis and the absence of RF (or anti-citrullinated antibodies).⁴

An important subgroup of patients with psoriatic arthritis has inflammatory spinal disease (spondylitis), which looks similar but is not identical to ankylosing spondylitis. Other forms of arthritis that may be difficult to distinguish from psoriatic arthritis include osteoarthritis and gout.⁴

See also the separate Acute Polyarthritis and Acute Monoarthritis articles.

• Rheumatoid arthritis.

• Reactive arthritis.

• Ankylosing spondylitis.

• Enteropathic arthropathy.

• Gout (particularly foot monoarthritis).

• Septic arthritis.

• Juvenile idiopathic arthritis and other causes of childhood arthritis.

Diagnosing psoriatic arthritis (investigations)

There are no 'clinching' confirmatory tests. Clinical and radiographic impressions are often sufficient to make the diagnosis in the presence of a classical rash.

• ESR and/or CRP will often be elevated.

• RF is usually negative but 5-10% of the general population have positive RF so its presence should not be used to rule out psoriatic arthropathy.

• Other autoimmune markers such as antinuclear factor (ANF) do not have any discriminatory value.

• It is not unusual for serum urate to be elevated in the acute phase and gout may co-exist with psoriatic arthritis.

• Synovial fluid aspirate should not show evidence of any crystals; however, the white cell count (predominantly neutrophils) is often significantly high.

• Serum immunoglobulin A (IgA) is elevated in about two thirds of sufferers but must be interpreted against a background elevation affecting about one third of those with uncomplicated psoriasis.

• HLA status may aid in diagnosis but needs to be interpreted with care, usually in a secondary care setting.

• X-ray changes classically associated with psoriatic arthritis include:
  

  • Mild bony erosion at the edge of cartilage.

  • Asymmetric erosive changes in the small joints of the hands and feet.

  • DIP or proximal interphalangeal (PIP) involvement - more common than metatarsophalangeal (MTP) or MCP changes.

  • DIP cases may have erosion and deformity with bony ankylosis of the joint and subluxation.

  • Erosion of the distal tuft of the distal phalanx.

• MRI/CT scanning may be more specific and sensitive in picking up subtle signs, particularly in the hands and feet, which indicate psoriatic arthropathy but need expert interpretation. MRI is useful for imaging the sacroiliac joint to detect inflammation/deformity.

Management of psoriatic arthritis¹⁰

Any person with suspected psoriatic arthritis should be referred to a rheumatologist for assessment and advice about planning their care.⁴

Non-pharmacological therapies, all with limited evidence include physiotherapy, occupational therapy, smoking cessation, weight loss, massage therapy and exercise. Physical exercise helps to maintain mobility and reduce stiffness.¹¹

Drug^{12 13}

In patients with psoriasis and psoriatic arthritis, monotherapy that addresses both skin and joint disease should be used in preference to multiple therapies. Methotrexate, retinoids and psoralen combined with ultraviolet A (PUVA) treatment appear to be most effective at treating skin and joints together.

• In patients with psoriatic arthritis, non-steroidal anti-inflammatory drugs (NSAIDs) may be used to relieve musculoskeletal symptoms.

• Local injections of corticosteroids should be considered as adjunctive therapy in psoriatic arthritis; systemic steroids at the lowest effective dose may be used but with caution. Oral corticosteroids may cause a rebound exacerbation of skin psoriasis when withdrawn.

• Disease-modifying antirheumatic drugs (DMARDs):
  

  • In patients with active disease (particularly those with many swollen joints, structural damage in the presence of inflammation, high ESR or CRP and/or clinically relevant extra-articular manifestations), treatment with disease-modifying drugs (such as methotrexate, sulfasalazine or leflunomide) should be considered at an early stage.

  • Antimalarial derived DMARDs such as hydroxychloroquine are usually avoided, as they may cause exfoliative dermatitis, worsening psoriasis.

• Biological treatments:
  

  • Etanercept, infliximab, adalimumab and golimumab are tumour necrosis factor (TNF) alpha inhibitors. NICE recommends that etanercept, infliximab, adalimumab or golimumab:^{14 15}
    

    • Should be offered as an option for treating adults with psoriatic arthritis when:
      

      • The person has arthritis with three or more tender joints and three or more swollen joints.

      • At least two other DMARDs, given on their own or together, haven't worked.

    • If the person's psoriatic arthritis has not shown a measured response at 12 weeks, then treatment should be stopped.

  • Apremilast is a selective inhibitor of phosphodiesterase 4 (PDE4) and inhibits spontaneous production of TNF-alpha. Apremilast, alone or in combination with DMARDs, is recommended as an option for treating active psoriatic arthritis in adults only if:¹⁶
    

    • They have peripheral arthritis with three or more tender joints and three or more swollen joints; and

    • Their disease has not responded to adequate trials of at least two standard DMARDs, given either alone or in combination.

  • Tofacitinib selectively inhibits the Janus-associated tyrosine kinases JAK1 and JAK3.Tofacitinib, with methotrexate, is recommended as an option for treating active psoriatic arthritis in adults, only if the person has had a tumour necrosis factor (TNF)-alpha inhibitor but their disease has not responded within the first 12 weeks or has stopped responding after 12 weeks, or TNF-alpha inhibitors are contra-indicated but would otherwise be considered.¹⁷

  • Ixekizumab is a human monoclonal antibody that binds to interleukin-17A and inhibits the release of pro-inflammatory cytokines and chemokines. Ixekizumab alone, or with methotrexate, is recommended as an option for treating active psoriatic arthritis in adults, only if the person has had a TNF-alpha inhibitor but their disease has not responded within the first 12 weeks or has stopped responding after 12 weeks, or TNF-alpha inhibitors are contra-indicated but would otherwise be considered.¹⁸

  • Certolizumab pegol is a fragment of a monoclonal antibody specific to TNF-alpha. Certolizumab pegol alone, or in combination with methotrexate, is recommended as an option for treating active psoriatic arthritis in adults only if the person has had a TNF-alpha inhibitor but their disease has stopped responding after the first 12 weeks.¹⁹

  • Secukinumab is a recombinant human monoclonal antibody that selectively binds to cytokine interleukin-17A (IL-17A) and inhibits the release of proinflammatory cytokines and chemokines. Secukinumab alone, or in combination with methotrexate, is recommended as an option for treating active psoriatic arthritis in adults only if the person has had a TNF-alpha inhibitor but their disease has not responded within the first 12 weeks or has stopped responding after 12 weeks, or TNF-alpha inhibitors are contra-indicated but would otherwise be considered.¹⁹

  • Ustekinumab (a cytokine modulator) is recommended as an option, alone or in combination with methotrexate, for treating active psoriatic arthritis in adults only when treatment with TNF-alpha inhibitors is contra-indicated but would otherwise be considered, or the person has had treatment with one or more TNF-alpha inhibitors.²⁰

  • Guselkumab is a recombinant human monoclonal antibody that blocks the activity of pro-inflammatory cytokines. NICE has published a technological appraisal for the use of guselkumab (alone or with methotrexate) for treating active psoriatic arthritis after inadequate response to DMARDs.²¹ However, this option should only be considered for patients who have:

    • Peripheral arthritis with three or more tender joints and three or more swollen joints.

    • Moderate to severe psoriasis (a body surface area of at least 3% affected by plaque psoriasis and a Psoriasis Area and Severity Index (PASI) score greater than 10).

    • Had two conventional DMARDs and at least one biological DMARD.

  • Upadacitinib is a selective and reversible inhibitor of the Janus-associated tyrosine kinase JAK1. NICE has recommended that upadacitinib, alone or in combination with methotrexate, should be an option for patients with psoriatic arthritis who:²²

    • Have peripheral arthritis with three or more tender joints and three or more swollen joints; and

    • Have failed to respond to or cannot tolerate two conventional DMARDs and at least one biological DMARD; or

    • Would otherwise be considered for TNF-alpha inhibitors but these are contra-indicated.

  • Risankizumab is a humanised monoclonal antibody that binds selectively to interleukin-23 and blocks the activity of pro-inflammatory cytokines. NICE has recommended risankizumab, alone or with methotrexate, as an option for treating active psoriatic arthritis in adults whose disease has not responded well enough to DMARDs or who cannot tolerate them. It is recommended only if patients have:²³
    

    • Peripheral arthritis with three or more tender joints and three or more swollen joints.

    • Moderate to severe psoriasis (a body surface area of at least 3% affected by plaque psoriasis and a Psoriasis Area and Severity Index [PASI] score greater than 10).

    • Had two conventional DMARDs and at least one biological DMARD.

  • Bimekizumab is a humanised monoclonal antibody that blocks the activity of pro-inflammatory cytokines. NICE has recommended the use of bimekizumab on its own or with methotrexate as an option for treating active psoriatic arthritis.¹ It can only be used in adults whose condition has not responded well enough to disease-modifying antirheumatic drugs (DMARDs) or who cannot tolerate them. Eligibility criteria is that adults can trial bimekizumab if they have had 2 conventional DMARDS such as ixekizumab and secukinumab and:

    • At least 1 biological DMARD or

    • Tumour necrosis factor (TNF)-alpha inhibitors are contraindicated but would otherwise be considered.

Surgery

Various surgical approaches are used to treat deformed joints for functional improvement. Chronic monoarticular synovitis can be improved by synovectomy, in combination with physiotherapy.

Complications of psoriatic arthritis

• These include joint destruction, finger destruction, disability, extra-articular complications such as eye disease and, rarely, aortitis (causes aortic insufficiency).

• Psoriatic arthritis can affect people's ability to work and carry out daily activities, which can have a substantial impact on quality of life.

• Atlanto-axial subluxation with attendant neurological complications can occur.

• Psoriatic arthritis is associated with an increased risk of cardiovascular disease.²⁴

Prognosis

• Psoriatic arthritis was initially considered to be a mild disease, but 40-60% of patients develop erosive and deforming joint complications, which not only lead to lower articular function and higher mortality but also affect patients' ability to work and affect their social relationships.

• Aggressive treatment of early-stage progressive psoriatic arthritis can help to improve prognosis.¹⁴