Which radiographic deformity is characteristic of psoriatic arthritis?

• A. Pencil-in-Cup Deformity
• B. Swan Neck Deformity
• C. Boutonniere Deformity
• D. Ulnar Deviation

Answer: (A)

The key radiographic pattern in psoriatic arthritis is the pencil-in-cup deformity. This result comes from erosive, asymmetric joint destruction that resorbs the distal portion of the finger bone, giving a slender, pencil-like distal phalanx that sits against a cup-shaped (cupped) appearance of the adjacent bone. This distinctive look on hand X-rays is a strong clue for psoriatic arthritis, especially when the changes are asymmetric and involve the small joints, often with DIP involvement. Other deformities like swan neck or boutonniere are more typical of different conditions, and while ulnar deviation can be seen in psoriatic arthritis, it is not the defining radiographic feature.