Ivory phalanx

Ivory phalanx is a finding of increased radiodensity of an entire phalanx as a result of periosteal and endosteal bone formation.

This sign is a unique and specific radiographic manifestation of psoriatic arthritis, yet it is uncommon and thus of low sensitivity. Nevertheless, it is of particular importance when articular abnormality or resorption of the tufts is absent. It is almost always associated with nail disease of the same digit.