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Classification of Joint Involvement in Psoriatic Arthritis
What are the characteristic patterns of joint involvement in Psoriatic arthritis?
Approximately 95% of patients with PsA have peripheral joint disease (synovitis, tenosynovitis [dactylitis], enthesitis).
Another 5% have axial spine involvement exclusively. In 1973, Moll and Wright divided PsA into five broad categories. These categories overlap, creating a heterogeneous combination of joint disease. For instance, only 2% to 5% of PsA patients have predominantly DIP involvement, whereas over 50% of patients have DIP involvement in association with another pattern. As mentioned earlier, 5% of patients have only axial spine involvement but up to 40% of patients with one of the other patterns of PsA will also have coexistent axial involvement. Importantly, these patterns are not mutually exclusive.
Classification of Joint Involvement in Psoriatic Arthritis
Subtype | % | Typical Joints |
---|---|---|
1. Asymmetric oligoarticular disease | 15–20 | DIP and PIP joints of hands and feet. MCP joints, MTP joints, knees, hips, and ankles |
2. Predominant DIP involvement | 2–5 | DIP joints |
3. Arthritis mutilans | 5 | DIP joints, PIP joints |
4. Polyarthritis “rheumatoid-like” | 50–60 | MCP joints, PIP joints, and wrists |
5. Axial involvement (isolated) | 2–5 | Sacroiliac, vertebral |
DIP , Distal interphalangeal; MCP , metacarpophalangeal; MTP , metatarsophalangeal; PIP , proximal interphalangeal.
What other features are associated with certain subtypes?
- • Asymmetric oligoarthritis—dactylitis.
- • Predominant DIP involvement—nail changes.
- • Arthritis mutilans—osteolysis of involved joints, “telescoping” of digits.
- • “Rheumatoid-like” disease—fusion of wrists.
- • Axial involvement—asymmetric sacroiliitis and “jug handle”-like syndesmophytes.