A 40-year-old White woman presents to her primary care physician and reports fatigue, overall stiffness, and arthralgia in her hands, feet, and left knee that has worsened over the past several months. At first, the joint pain and stiffness were worse in the morning but improved with activity. Now, she experiences both all day long and says it has greatly affected her overall physical functioning.

She has a history of psoriasis (since her 20s), primarily on her scalp but also on her shin, elbows, and arm. Her medical history is otherwise unremarkable.

Physical exam reveals a patch of psoriasis on her scalp as well as silvery scaling on a sharply marginated and reddened area on her outer right arm, below the elbow. There is severe fixed flexion deformity of the interphalangeal joints of her right hand as well as dactylitis of each digit. The nails of this hand show pitting, transverse depressions, and subungual hyperkeratosis, with some pitting in the nails of the left hand as well. There is also dactylitis and some flexion deformity in the toes of the left foot, with mild dactylitis in the right foot.

Laboratory testing is performed and shows increased serum immunoglobulin A as well as elevated erythrocyte sedimentation rate. She is negative for both rheumatoid factor and antinuclear antibodies.