Which deformity is characteristic of rheumatoid arthritis?

Swan neck deformities are indeed a characteristic feature of rheumatoid arthritis. This deformity typically presents as a flexion of the metacarpophalangeal joint and hyperextension of the proximal interphalangeal joint, which results in a distinct appearance of the fingers reminiscent of a swan neck. It occurs as a result of the imbalance in muscle forces around the affected joints, often caused by the underlying inflammation and damage to the joint structures associated with rheumatoid arthritis.

In contrast, Heberden's nodes and Bouchard's nodes are associated with osteoarthritis. Heberden's nodes are bony growths that develop on the distal interphalangeal joints, while Bouchard's nodes occur on the proximal interphalangeal joints, neither of which are characteristic of rheumatoid arthritis. Claw hand is a deformity typically seen in conditions involving ulnar nerve palsy or other neuropathic conditions, not specifically related to rheumatoid arthritis.