A 56-year-old woman presents complaining of arthralgia in her hands, stiffness in the distal joints, and general fatigue. These symptoms have persisted for some time, but only in the past few months has she noticed that her symptoms linger for a long time and seem to worsen with rest. She is also reporting compromised function of her hands in day-to-day activity (she is right-handed), such as opening jars and zipping up her jacket, as well as changes in her nails. She is seeking treatment for a fungal nail infection.

Physical examination reveals joint swelling and sausage digits in her hands, although more so in the right hand, as well as slight deformity of the fingers. Cracking of the edges of her nails is evident, as is nail pitting, transverse depressions in many of her nails, and subungual hyperkeratosis. Skin examination reveals several patches of scaly erythematous plaques on her scalp and around the umbilicus.

Family history reveals that the patient's mother had severe psoriasis during her (the patient's) childhood. Otherwise, her medical history is unremarkable. Laboratory tests reveal elevated serum immunoglobulin A, erythrocyte sedimentation rate, and C-reactive protein. Rheumatoid factor and antinuclear antibody are negative.