“Pencil-in-cup” deformity is a rare bone disorder primarily associated with a severe form of psoriatic arthritis (PsA) called arthritis mutilans.

Pencil-in-cup sign is sometimes called pencil-in-cup change or deformity. It’s an abnormal change in one of the small hinge-like joints of your fingers or toes. It happens when new bone begins ...

A pencil-in-cup deformity is just one possible form that bone and joint destruction can take in arthritis mutilans. You won’t know you have this type of damage unless your doctor sees it on an X ...

Arthritis mutilans is a rare form of psoriatic arthritis. It typically affects your fingers and toes, deforming and curling them in a condition called s, or pencil-in-cup deformity.