Differential Diagnosis of Psoriatic arthritis
What clinical features suggest PsA rather than other polyarticular arthritic diseases such as rheumatoid arthritis?
- Asymmetric, often oligoarticular joint involvement.
- Absence of rheumatoid factor.
- Significant nail pitting or nail dystrophy.
- Involvement of DIP joints in the absence of osteoarthritis.
- “Sausage digits” (dactylitis): seen in 30% to 50%. Due to synovitis and flexor tenosynovitis.
- Enthesitis: seen in 35% to 40%. Most common sites: Achilles and plantar fascia insertion.
- Family history of psoriasis or PsA.
- Axial radiographic evidence of sacroiliitis, paravertebral ossification, and syndesmophytes.
- Peripheral radiographic evidence of erosive arthritis with relative lack of periarticular osteopenia.
- Synovial biopsies show increased vascularity and the presence of macrophages (CD163+), lymphocytes, and neutrophils.
