Psoriatic arthritis

• Psoriasis affects 1% of the population 
• 5% of patients with psoriasis will develop psoriatic arthropathy
• 15-20% of adults will develop joint disease before skin lesions appear
• people with severe arthritis can have little or no skin disease, and vice versa
• flare-ups of symptoms do not necessarily coincide
• The condition has a genetic component:
  • HLA-DR4 is a risk factor for psoriatic and rheumatoid arthritis
  • patients with psoriatic spondylitis share HLA-B27 with other spondylitic patients

Clinical features

• Skin
  • Most commonly, psoriasis, a skin disease, appears first, followed by psoriatic arthritis. However, in a minority of cases, joint problems can start before any skin manifestations appear.
  • The severity of the skin disease does not predict the severity of the joint disease.
  • Plaque psoriasis (Well-demarcated erythematous plaques with silvery scale) is the most common form of skin psoriasis seen with psoriatic arthritis. Joint symptoms may be exacerbated by a flare in skin psoriasis but quite commonly the skin symptoms behave independently of joint symptoms.
  • Most people with psoriatic arthritis have mild psoriasis.

• Joints :
  • 5 Subtypes:
    • Oligoarticular arthritis: Asymmetric, <5 joints involved -Most common – 60% of cases
    • Polyarticular arthritis: Symmetric, resembles rheumatoid arthritis, negative for rheumatoid factor.
    • Distal arthritis: Prominent DIP joint involvement.
    • Arthritis mutilans: Severe, destructive joint disease causing deformities.
    • Spondyloarthritis: Involves sacroiliitis and spondylitis, with or without peripheral joint disease.
• Dactylitis – are characteristic of psoriatic arthritis in the hands enthesitis 
  • differentials below
• Nail disease – severity of nail disease correlates with the severity of both skin and joint diseas
  • transverse or longitudinal ridging
  • discolouration
  • subungual hyperkeratosis
  • onycholysis
  • pitting
  • splinter hemorrhages
• Eyes
  • Conjunctivitis, iritis
• Heart and lung (late findings)
  • Aortic insufficiency
  • Apical lung fibrosis
• Peripheral NS
  • Cauda equina claudication

Investigations

• are no diagnostic blood tests for psoriatic arthritis but tests may be done to help confirm the diagnosis and rule out other causes
  • WBC – usually raised
  • ESR and CRP – usually raised
  • Hypergammaglobulinaemia
  • Rheumatoid factor –  usually negative but may be positive in up to 10% of patients with psoriatic arthritis
  • Anti-CCP – usually negative but may be positive in up to 7% of patients with psoriatic arthritis.
  • HLA-B27 testing

• Imaging : Xray
  • Erosive changes of the DIP seen in radiography may be used as both a sensitive and specific diagnostic feature of psoriatic arthritis 
  • joint erosions and joint space narrowing
  • bony proliferation including periarticular and shaft periostitis,
  • osteolysis including “pencil in cup’ deformity,
  • acro-osteolysis
  • ankylosis
  • spur formation
  • spondylitis

• Other conditions with similar clinical and X-ray findings to psoriatic arthritis include:
  • Rheumatoid arthritis (RA)
  • Gout
  • Osteoarthritis (OA)
  • Reactive arthritis(ReA)
  • Ankylosing spondylitis (AS)
  • but Psoriatic arthritis shares features with RA, ReA, AS but has distinct characteristics like DIP joint involvement and asymmetric sacroiliitis.

Treatment Approaches

• mild cases
  • NSAIDs
• moderate cases
  • csDMARDs (like Methotrexate, Sulfasalazine),
• severe cases
  • bDMARDs (TNF inhibitors, IL-17 inhibitors)
  • tsDMARDs (JAK inhibitors, PDE-4 inhibitors).

Disease Monitoring:

• Regular assessment of disease activity
  • using tender and swollen joint counts
  • BASDAI
  • Health-related QoL measures, and other composite indices.

Non-Pharmacological Treatment

1. Education: regarding the disease and about joint protection
2. Physical Therapy: Tailored exercises to improve joint function and reduce pain.
3. Occupational Therapy: Strategies for daily activities to minimize joint stress.
4. Weight Management: Maintaining a healthy weight to reduce stress on joints.
5. Exercise: Regular, moderate exercise to maintain joint flexibility and muscle strength.
6. Dietary Adjustments: Anti-inflammatory diet may help reduce symptoms.
7. Stress Management: Techniques like meditation or yoga to manage stress which can exacerbate PsA symptoms.
8. Heat and Cold Therapy: To relieve pain and reduce inflammation.
9. Assistive Devices: Tools to help with mobility and daily tasks.
10. Education and Support: Understanding the condition and finding support groups.

prognosis 

• Psoriatic arthritis can be an aggressive disease impacting quality of life.
• Most people with psoriatic arthritis will have ongoing problems with arthritis throughout the rest of their life.
• Remissions are uncommon; occurring in less than 20% of patients with less than 10% of patients having a complete remission off all medication with no signs of joint damage on X-rays.
• People with severe psoriatic arthritis have been reported to have a shorter lifespan than average.

Features associated with a relatively good prognosis are:

• Male sex
• Fewer joints involved
• Good functional status at presentation
• Previous remission in symptoms.

Features associated with a poor prognosis include:

• ESR > 15 mm/hr or raised CRP at presentation
• Failure of previous medication trials
• Absence of nail changes
• Joint damage (clinically or radiographically)
• HLA-B27-, -B39-, or -DQw3-positive status.

Dactylitis – differentials

1. Infection-Related Dactylitis:
   • Blistering distal dactylitis: Common in children, caused by streptococcus or staphylococcus.
   • Tuberculous dactylitis: Rare, a form of osteomyelitis in hands and feet, linked to tuberculosis.
   • Syphilitic dactylitis: Associated with congenital syphilis, bilateral and symmetrical involvement.
2. Spondyloarthritis:
   • Common in psoriatic arthritis, reactive arthritis, ankylosing spondylitis.
   • Indicates disease severity in psoriatic arthritis, often affecting feet.
3. Other Conditions:
   • Gout: Up to 5% incidence, related to urate crystal deposition.
   • Sarcoidosis: Rare, associated with lupus pernio, causes bilateral finger swellings.
   • Sickle-cell dactylitis: Common in sickle-cell anemia, especially in early childhood, often the first sign of the disorder.