A 40-year-old woman presents with pain and swelling of the distal interphalangeal (DIP) joints of her fingers. She states that symptoms have been intermittent for the past 6 months but have gotten worse over the past several weeks, with associated morning stiffness lasting about 1 hour. She had plantar fasciitis of the left foot about 4 months ago. Her mother had psoriasis, which was treated with adalimumab.

On physical examination, she has pitting of her fourth and fifth fingernails, with onycholysis. Her eyes show no inflammation. Peripheral articular examination shows pain and swelling in the first, second, and fourth DIP joints bilaterally. Laboratory results reveal negative rheumatoid factor (RF), antinuclear antibody, and anticitrullinated protein antibody. HLA-B27 is positive.

A radiograph shows a "pencil-in-cup" abnormality in the DIP joints of the first and second fingers plus early changes in the DIP joint of the fourth finger.