A patient with psoriatic arthritis develops a 'sausage digit' (dactylitis) of the index finger. In addition to DMARDs/biologics, the deformity of the DIP joint that is characteristic of psoriatic arthritis (and NOT seen in RA) and that may require surgical intervention is:

• A Arthritis mutilans with telescoping (opera-glass) deformity due to severe osteolysis ✓
• B Boutonnière deformity at the PIP joint
• C Swan neck deformity at the PIP joint
• D Ulnar drift of the fingers at the MCP joints

Explanation

Arthritis mutilans is a severe, destructive form of psoriatic arthritis (also seen in reactive arthritis) in which aggressive osteolysis of the phalanges leads to bone resorption at multiple joints, causing the classic 'opera-glass' (main en lorgnette) deformity — the digit can be telescoped inward and pulled outward. This is NOT a feature of RA. Boutonnière, swan neck deformities, and ulnar drift are characteristic RA deformities. In arthritis mutilans, surgical options include arthrodesis of individual joints or silastic implant arthroplasty where some motion is desired, but outcomes are challenging given the diffuse bone loss.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.