A 45-year-old White woman presents to her doctor for pain and reduced function in her legs and feet. Over the past 6 months, the patient has noted a significant reduction in her overall quality of life. In addition to pain in her legs and feet, she has difficulty managing tasks during the day that involve walking, climbing stairs, and carrying heavier objects. She reports no pain relief with the use of nonsteroidal anti-inflammatory drugs (NSAIDs). She has a history of psoriasis, which was diagnosed at age 20, and psoriatic arthritis (PsA), which was diagnosed 5 years ago. She has been on treatment with methotrexate since her PsA diagnosis. Her history is otherwise unremarkable, and she takes no other medications.

Physical exam reveals minimal skin involvement with only two small scaly, erythematous ~3 cm patches on the patient's scalp and one nickel-sized spot around the umbilicus. There is pitting of three fingernails. Tenderness is detected in the entheseal sites around the ankles bilaterally, particularly in the right ankle, with no swelling, as well as tenderness around the right knee. Her vital signs are normal. Laboratory testing reveals elevated erythrocyte sedimentation rate and C-reactive protein level.