psoriatic arthritis

Introduction

Psoriatic arthritis develops in <30% of patients with psoriasis.

Classification

5 clinical groups:

• predominant distal interphalangeal joint (DIP) arthritis in hands & feet associated with nail involvement
• arthritis mutilans, severely destructive athritis involving the hands with shortening of the digits
• symmetrical polyarthritis involving both large & small joints, resembling seronegative rheumatoid arthritis
• asymmetrical oligoarthritis involving large joints primarily in the lower extremities
• psoriatic spondylitis (HLA-B27 positive 50-75%)

Epidemiology

• 15-20% of patients with psoriasis; < 30%

Pathology

• inflammation involves the tenosynovial junction causing edema beyond the affected joints (sausage digits)
• erosions can be much more destructive than osteoarthritis
• HIV1 infection associated with increased severity of psoriatic arthritis

Genetics

• mutations or gene deletions of junB
• polymorphisms in TNF-alpha are a cause of susceptibility psoriatic arthritis
• polymorphisms in lymphotoxin-alpha (LTA) are a cause of susceptibility psoriatic arthritis
• other implicated genes: MICA

Clinical manifestations

• a prodromal phase of nonspecific musculoskeletal symptoms with visits to primary care or emergency department
• cutaneous psoriasis
  • generally precedes arthritis
    • arthritis may precede cutaneous psoriasis by up to 10 years
  • strong confirmatory sign, but may not be present
  • plaque psoriasis on extensor surfaces, scalp, posterior auricular region, umbilicus, gluteal fold
  • pustular psoriasis on palms & soles
  • nail pitting, onycholysis
• asymmetric oligoarthritis or symmetric polyarthritis
  • asymmetric lower extremity oligoarthritis
  • symmetric arthritis of DIP joints in hands & feet
    • DIP involvement associated with nail involvement
    • arthritis mutilans
  • symmetric arthritis of PIP joints, MCP joints & MTP joints
  • may be diffuse dactylitis (sausage digits)
    • dactylitis predicts a more severe disease phenotype in early disease
    • predicts more swollen joints, higher serum CRP, synovitis & bone erosions
• tendonitis, tenosynovitis & enthesitis (heel pain)
• axial involvement
  • spondylitis may occur at any level
    • may skip regions, may be asymmetric
  • sacroiliitis is a strong confirmatory sign
    • may not be present
  • may start in cervical spine
• extent of skin disease does NOT correlate with severity of arthritis
• explosive onset or severe flare of arthritis suggests HIV1 infection
• conjunctivitis more common than anterior uveitis
  • 80% of uveitis is anterior (iritis), 20% posterior
• no relationship between extent of skin & joint disease

* see classification for different patterns

Diagnostic criteria

• arthritis: asymmetric oligoarthritis or symmetric polyarthritis
• plus >= 3 of the following
  • psoriasis
  • psoriatic nail dystrophy
  • rheumatoid factor negative
  • dactylitis
  • radiographic evidence of juxta-articular new bone formation (joints of hands &/or foot)

Laboratory

• erythrocyte sedimentation rate (ESR) is increased
• rheumatoid factor (RF)
  • generally negative or low titer
  • positive RF with high titer suggest coexistant rheumatoid arthritis
• association with HLA-B27; however, HLA-B27 is negative in most patients
• serum uric acid may be elevated because of rapid turnover of skin cells
• HIV serology

Radiology

• X-ray of hands
  • destructive arthritis with erosions & osteophytes
  • arthritis multilans
    • distal interphalageal joint involvement
  • lysis of terminal phalanges
  • marked osteolysis & ankylosis
  • new bone formation at proximal head of distal phalanx
    • 'pencil in a cup' appearance
• X-ray of spine, sacrum, ilium
  • bone spurs (osteophytes)
  • syndesmophytes
  • sacroiliitis

Complications

• increased risk of fracture
  • prevalence of osteopenia & osteoporosis similar to that of the general population
• hyperuricemia & gout are comorbidities associated with psoriasis & psoriatic arthritis
  • infectious arthritis is less common than gout
• increased risk of cardiovascular disease
  • increased risk for cardiovasacular mortality (RR=1.2)
• increased risk of respiratory mortality (RR=3.4) & infection (RR=2.4)
• no increased risk of overall mortality

• disease interaction(s) of HIV1 infection with psoriatic arthritis

Differential diagnosis

• rheumatoid arthritis
• ankylosing spondylitis
• reactive arthritis
• enteropathic arthritis
• gout, pseudogout
• inflammatory erosive osteoarthritis
• explosive onset or severe flare of psoriatic arthritis suggests comorbid HIV1 infection

Management

• ibuprofen, indomethacin or other NSAID
  • may be useful for mild forms of psoriatic arthritis
  • does not alter course of disease
• glucocorticoid injections for limited arthritis
• DMARDS useful for treating arthritis & enthesitis
  • methotrexate, start with 7.5 mg PO QD (hepatotoxic, avoid in alcoholics)
  • auranofin, start with 3 mg PO QD
  • hydroxychloroquine unlikely to benefit psoriatic arthritis & may exacerbate psoriasis
  • azathioprine
• TNF-alpha inhibitor for methotrexate-resistant disease
  • etanercept
  • infliximib
  • adalimumab
  • certolizumab
  • golimumab
  • TNF-alpha inhibitor + methotrexate
• brodalumab (Siliq) or secukinumab (IL17RA inhibitors)
  • secukinumab (Cosentyx) may be of benefit
• ustekinumab (IL12 & IL23 inhibitor)
  • not recommended (NICE)
• tofacitinib (Xeljanz) FDA approved
  • symptomatic benefit
  • effect on radiologic progression unclear
  • may be of benefit in patients with inadequate response to TNF-alpha inhibitor
• guselkumab (Tremfya)
• NSAIDs, antimalarials & withdrawal from glucocorticoids may aggravate psoriasis
• tight control of psoriatic arthritis with DMARDs +/- TNF-alpha inhibitor more effective than standard care but with more serious adverse effects & expense
• weight reduction & smoking cessation may reduce disease activity

More general terms

• spondyloarthropathy
• psoriasis
• chronic inflammation

More specific terms

• arthritis mutilans

Additional terms

• sacroiliitis
• spondyloarthropathy (HLA B27-associated arthritis, seronegative spondyloarthropathy)

Patient information

psoriatic arthritis patient information

Database

• OMIM: https://mirror.omim.org/entry/