- Type of seronegative spondyloarthropathy
The etiology and pathogenesis of psoriatic arthritis are not fully understood but involves a complex interaction between genetic and environmental factors resulting in immune-mediated inflammation involving the skin and joints and may involve other organs.
Genetic factors:Approximately 33 to 50% of psoriatic arthritis patients have at least one first degree relative who also has psoriasis or psoriatic arthritis. The genetic associations with psoriatic arthritis and psoriasis are not identical so that some genes associated with psoriatic arthritis are not associated with psoriasis, and the same is true for psoriasis. Also, certain genes are associated with specific phenotypes of psoriatic arthritis.
- HLA genes: Involved in antigen presentation and immune recognition
- Symmetric polyarthritis: HLA-DR4
- Axial involvement: HLA-B27
- Non-symmetric polyarthritis: HLA-B38 & HLA-B39
- Psoriasis susceptibility region 1 (PSORS1): HLA-B57:01 and HLA-C06:02
- Psoriasis has a stronger association than psoriatic arthritis with this region
- Non-HLA genes: Involved in immune activation and inflammation including intracellular signaling, cytokine expression, and signaling, and T cell effector function.
- IL-12B: Associated with psoriasis but not psoriatic arthritis.
- Streptococcal infection and recent antibiotic exposure
- Koebner phenomenon: Skin trauma is known to induce flares of psoriatic skin lesions
- Internal/deep Koebner phenomenon: Joint trauma may induce a flare of arthritis
- Tobacco: Trigger for rheumatoid arthritis in patients with certain HLA-DR genes, appears to be protective for the development of psoriatic arthritis
The clinical manifestations are varied and can change over time, evolving from one articular pattern to another.
- Peripheral arthritis: Oligoarticular vs. polyarticular pattern
- Enthesitis: Inflammation around the insertion of ligaments, tendons, or joint capsules
- Dactylitis: Swelling of entire digit/finger/toe “sausage digit”
- Axial disease: Involving sacroiliac joints, usually asymmetric and spondylitis with discontinuous involvement with bulky non-marginal syndesmophytes
- Psoriatic skin disease: Usually presents before the onset of arthritis but can occur simultaneously and even before the onset of joint disease. The severity of skin disease does not correlate well with the severity of the articular disease.
- Psoriatic nail disease: Onycholysis, pitting, and splinter hemorrhages. The severity of nail disease correlates with the severity of both skin and joint disease. It is present in 80 to 90% of patients with psoriatic arthritis and is associated with DIP joint involvement.
- Psoriatic Ocular disease: Uveitis but unlike that associated with ankylosing spondylitis, it is often chronic, bilateral, and often involves posterior elements.
- Acute phase reactants: Elevated as in most inflammatory diseases
- ESR (erythrocyte sedimentation rate)
- CRP (C-reactive protein)
- Seronegative arthropathy findings:
- RF and anti-CCP antibodies classically absent
CASPAR criteria (Classification of Psoriatic Arthritis):Most accepted classification criteria for psoriatic arthritis; in use since 2006
Radiographic findings:Findings are driven by bone destruction and pathologic new bone formation often in the same digit or even the same joint, which is a characteristic feature of psoriatic arthritis; bone destruction with bone production. Despite treatment with DMARDs (disease-modifying anti-rheumatic drugs), psoriatic arthritis results in radiographic damage in about 47% of patients during the first two years of the disease.
Peripheral arthritis findings:Characteristic pattern of erosive changes, gross joint destruction, joint space narrowing is seen.
- Erosive changes (including MCP, PIP, DIP joints, and wrists)
- New bone formation
- Bony ankylosis
- Joint osteolysis
- “Pencil-in-cup” deformity
Entheseal involvement:Characteristic in all spondyloarthropathies
- Erosions and new bone formation
Axial features:The features which differentiate psoriatic arthritis from ankylosing spondylitis are the asymmetric and often unilateral presentation of sacroiliitis. Syndesomophytes in psoriatic arthritis are often bulkier, asymmetric, and discontinuous skipping vertebral levels.
- Sacroiliitis and spondylitis
- Syndesmophytes (ossification of the annulus fibrosis)
- Rheumatoid arthritis
- Reactive arthritis
- Gouty arthritis
- Systemic lupus erythematosus
- Inflammatory bowel disease-associated arthritis
- Non-pharmacologic therapies: Physical therapy & occupational therapy, smoking cessation, weight loss, exercise
- Symptomatic management: NSAIDs, glucocorticoids
- Oral small molecules (OSMs): Methotrexate, sulfasalazine, cyclosporine, leflunomide, apremilast
- Tumor necrosis factor inhibitor (TNFi) biologics: Etanercept, infliximab, adalimumab, golimumab, certolizumab pegol
- IL-12/23 inhibitor biologic: Ustekinumab
- IL-17 inhibitor biologics: Secukinumab, ixekizumab, brodalumab
- CTLA4-immunoglobulin: Abatacept
- JAK inhibitor: Tofacitinib
Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) recommendations: