Table 1.

Differentiating rheumatoid arthritis (RA) and psoriatic arthritis (PsA)

FeaturesPsARA
Number of joints involved30–50% with oligoarthritisPredominant polyarthritis
Joint involvementAny joint, including distal interphalangeal jointsUsually distal interphalangeal joint sparing
EnthesitisTypical, clinically present in 60–80%Not typical
DactylitisPresent in 30%Not typical
Axial involvementAxial spondyloarthritis phenotypeErosive cervical disease
Skin/nail diseasePsoriasis in 80%, nail disease in 60%Background population risk or lower
SerologyUsually RF and CCP negativeUsually RF and/or CCP positive
Typical radiographic changesPeriosteal new bone formation (uncommon especially in early disease)Erosion and osteopenia
  • CCP = cyclic citrullinated peptide; RF = rheumatoid factor