What is the diagnosis and work-up for psoriatic arthritis and autoimmune arthritides?

Diagnosis and Work-up for Psoriatic Arthritis and Autoimmune Arthritides

The diagnosis of psoriatic arthritis (PsA) should follow the CASPAR (Classification Criteria for Psoriatic Arthritis) criteria, with a comprehensive evaluation including joint assessment, laboratory tests, and imaging to identify inflammatory musculoskeletal disease. 1

Diagnostic Criteria and Initial Assessment

• PsA is an inflammatory seronegative spondyloarthropathy affecting up to one-third of patients with psoriasis, with 80% of patients developing skin manifestations before joint symptoms 2, 3
• Diagnosis should ideally involve both dermatology and rheumatology expertise to confirm psoriasis and inflammatory musculoskeletal disease respectively 1
• CASPAR criteria are the standard for diagnosis, focusing on inflammation features including joint pain, spine/enthesis involvement with erythema, warmth, swelling, and prominent morning stiffness 1

Core Assessment Domains

Baseline evaluation of PsA should include the following domains:

• Peripheral joint assessment: Examination of 68 joints for tenderness and 66 joints for swelling 1
• Pain evaluation: Patient-reported assessment using visual analogue or category rating scales 1
• Patient global assessment of disease activity 1
• Physical function measurement using validated tools such as Health Assessment Questionnaire (HAQ) 1
• Health-related quality of life assessment using general (SF-36) or PsA-specific measures (PsAQoL) 1
• Fatigue assessment through patient self-report or instruments like FACIT 1
• Laboratory tests including acute phase reactants (CRP, ESR) 1
• Radiographic assessment based on clinical manifestations and physician judgment 1

Clinical Features and Manifestations

PsA has distinct clinical presentations that should be evaluated:

• Peripheral arthritis: Asymmetric joint involvement, often affecting distal interphalangeal joints 2, 4
• Dactylitis ("sausage digit"): Combination of enthesitis and synovitis involving an entire digit 1, 4
• Enthesitis: Inflammation at tendon, ligament, or joint capsule insertion sites, commonly at plantar fascia and Achilles tendon 1, 4
• Axial involvement: Spinal inflammation similar to ankylosing spondylitis 2, 4
• Nail disease: Commonly associated with PsA, especially with DIP joint involvement 1, 4

Laboratory and Imaging Studies

• Laboratory tests: ESR and CRP to assess inflammation; rheumatoid factor is typically negative (seronegative arthritis) 1
• Radiographic assessment: May reveal asymmetric sacroiliitis, spinal disease, joint erosions, new bone formation, ankylosis, or osteolysis (pencil-in-cup deformity) 2, 4
• Advanced imaging: MRI or ultrasound may be helpful for early detection of enthesitis and synovitis when conventional radiographs are normal 4

Poor Prognostic Factors

Factors associated with poor prognosis and progressive joint damage include:

• Polyarticular disease (high number of actively inflamed joints) 1
• Elevated ESR 1
• Previous treatment failures 1
• Existing joint damage (clinical or radiographic) 1
• Diminished quality of life as measured by standardized tools 1

Screening and Early Detection

• Dermatologists should actively screen all psoriasis patients for PsA at each visit, as early detection and treatment can prevent irreversible joint damage 1, 3
• Screening tools and simple physical examination maneuvers can help identify early PsA in dermatology clinics 3, 4
• Multidisciplinary care in combined dermatology-rheumatology clinics has been shown to improve diagnostic accuracy and optimize treatment approaches 5

Comorbidity Assessment

PsA is associated with multiple comorbidities that should be evaluated:

• Cardiovascular disease risk factors (hypertension, hyperlipidemia, diabetes) 1, 5
• Metabolic syndrome components 1
• Inflammatory bowel disease 1
• Depression and anxiety 1
• Liver disease (non-alcoholic fatty liver disease) 1

Treatment Response Assessment

• Treatment response for peripheral arthritis can be evaluated using criteria developed for rheumatoid arthritis, such as the 28-joint Disease Activity Score (DAS28) and European League Against Rheumatism (EULAR) response criteria 1
• For axial disease, the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) may be used to measure disease activity and treatment response 1

Early diagnosis and appropriate treatment are essential to prevent irreversible joint damage, reduce morbidity, and improve quality of life in patients with PsA 1, 4.