• Diagnosis is based on clinical history & physical examination
  
  • Presence of skin & nail lesions of psoriasis
  • Specific patterns of joint inflammation including distal arthritis, asymmetric oligoarthritis, symmetric polyarthritis, arthritis mutilans & spondyloarthritis (sacroiliitis & spondylitis)
  • Mixture of subtypes & pattern of disease may vary over time
  • Joint stiffness lasting for >30-45 min in the morning or after long periods of inactivity (eg sleep or travel)
  • Inflammatory back pain is an important clinical symptom in patient w/ axial disease
  • Other manifestations are enthesitis (inflammation at the tendon/bone interface), tenosynovitis & dactylitis (inflamed & swollen digit or “sausage digit”)

• Criteria used for the diagnosis of psoriatic arthritis:
  
  • Classification Criteria for Psoriatic Arthritis (CASPAR)

Classification Criteria for Psoriatic Arthritis (CASPAR)
Patient w/ established inflammatory articular arthritis, that is manifested by prolonged morning or immobility-induced stiffness, tender & swollen joints, w/ >3 points from features below	Points
Current psoriasis Personal history of psoriasis (unless there is presence of current psoriasis) Family history of psoriasis (unless there is presence of current or personal history of psoriasis) Current dactylitis or history of dactylitis recorded by a rheumatologist Juxta-articular new bone formation Negative rheumatoid factor Typical psoriatic nail dystrophy including onycholysis, pitting, & hyperkeratosis	2 1 1 1 1 1 1
Modified from: Taylor W, Helliwell P, Marchesoni A, et al. Classification criteria for psoriatic arthritis: development of new criteria from a large international study. Arthritis Rheum. 2006;54:2665-2673.

 

Moll & Wright Criteria for Psoriatic Arthritis

Patient w/ psoriasis & inflammatory arthritis, seronegative for rheumatoid arthritis & presenting w/ 1 of the 5 clinical subtypes below: Polyarticular, symmetric arthritis - Affects about 15% of psoriatic arthritis patients - Involves multiple symmetric pairs of joints in the hands & feet - Resembles rheumatoid arthritis  Oligoarticular (<5 joints), asymmetric arthritis - Most common type of psoriatic arthritis found in 80% of patients - Usually involves <5 joints & may affect any joints - Hands & feet may have enlarged "sausage digits" Distal interphalangeal joint involvement - Classic type occurs in about 5% - Involves distal joints of the fingers & toes - Nail changes are common Spondylitis predominant - Inflammation of the spinal column causing stiff neck, lower back pain, & sacroiliac pain - Peripheral disease may be seen in the hands, arms, hips, legs & feet Arthritis mutilans - Severe, deforming type of psoriatic arthritis affecting <5% - Affects a few joints in the hands & feet - Associated w/ pustular psoriasis

Modified from: Moll JM, Wright V. Psoriatic arthritis. Semin Arthritis Rheum. 1973;3:55-78.

Quality of Life

• Specific scales such as Psoriatic Arthritis Quality of Life index or more generic instruments (eg short form-36, Health Assessment Questionnaire & Functional Assessment of Chronic Illness Therapy) are used to assess the quality of life of patients w/ psoriatic arthritis
  • These tools are valid, reliable & responsive to change

Serology

• No specific serologic tests to confirm the diagnosis of psoriatic arthritis
• Absence of rheumatoid factor aid in the diagnosis

Plain radiography

• Helps in the diagnosis of psoriatic arthritis
• Demonstrates the extent & location of joint damage & distinguish psoriatic arthritis from other types of arthritis
• X-ray features of psoriatic arthritis:
  
  • Joint erosions that usually starts at the margins of the joints & then progresses toward the center
  • Joint space narrowing
  • Bony proliferation including periarticular & shaft periostitis
  • Osteolysis w/c includes “pencil in cup” deformity, acro-osteolysis, ankylosis, spur formation, & spondylitis
  • Distal interphalangeal erosive changes
  • Dactylitis affecting the feet in an asymmetric distribution 

• Changes occur early in the course of psoriatic arthritis
• Spectrum of joint inflammation is great w/c ranges from axial to peripheral disease, synovial & adjacent sot tissue inflammation, enthesitis, osteitis, new bone formation, & severe osteolysis along w/ overlapping findings
• Can be used to monitor the efficacy of treatment

Magnetic Resonance Imaging & Computed Tomography Imaging

• For detecting patients w/ asymptomatic disease
• Helps in the diagnosis of early sacroiliitis w/ no radiographic changes in plain X-ray
• Can detect erosions earlier in the course of disease

Ultrasonography

• Alternative method to estimate the degree of joint inflammation & volume of inflamed tissue
• More sensitive in detecting knee synovitis & lower extremity enthesopathy
• May also be used during ultrasound-guided aspiration/injection

• Patient-administered screening questionnaires such as Psoriasis Epidemiology Screening Tool (PEST), Psoriatic Arthritis Screening & Evaluation Tool (PASE), & Toronto Psoriatic Arthritis Screen (ToPAS) may be used for early detection of psoriatic arthritis in primary care or dermatology clinics

Course of the Disease

• Course of psoriatic arthritis varies ranging from mild & nondestructive to a severe, debilitating, erosive arthropathy
  • Erosive & deforming arthritis occurs in 40-60% of patients & may be progressive as early as w/in the 1st yr of diagnosis
  • Characterized by flares & remissions
  • Can have persistent inflammation, progressive joint damage, severe physical limitations, disability, & increased mortality, if left untreated 
• Patients are at increased risk of comorbid conditions such as diabetes mellitus, hypertension, coronary heart disease, inflammatory bowel disease, lymphoma, & depression
• Adverse prognostic factors include ≥5 swollen joints, increased CRP of >3 mnths, history of use of oral corticosteroid and/or structural joint damage due to disease