A 35-year-old White man presents to his primary care physician for his annual checkup. He reports increased fatigue, stiffness, and skeletal pain over the past year. He particularly complains about back pain on arising in the morning, which seems to get better when he is up and moving around. He also reports pain in his hands and fingers, which appear to be swollen, and is seeking treatment for what he believes to be a fungal infection of the nails. The patient is a carpenter and works extensively with his hands, often outdoors. His eyes are red and irritated, which he attributes to his pollen allergy and working in an environment with a lot of airborne particles, like sawdust.

Physical exam reveals symmetric polyarthritis (more than five digits) with dactylitis of the fingers in both hands, with pain along the flexor tendons. There is some ridging, pitting, and slight yellowing of the nails. Blood pressure is 120/70 mm Hg. Resting heart rate is 63 beats/min. He is 6 ft, 180 lb, BMI 24. Heart, breath, and gastrointestinal sounds are all normal on auscultation. There is no lymphadenopathy. Liver and spleen are normal on palpation. His eyes are red and watery, consistent with conjunctivitis. There is a scaly patch of skin about 5 cm wide on his right elbow, which he describes as a "stubborn patch of dry skin." He notes that he has never had any skin issues until now.

The patient's medical history is unremarkable, with no other comorbidities or medications. He is a nonsmoker. Family history reveals psoriasis on the maternal side, both in his mother and grandmother. Laboratory testing reveals serum IgA 500 mg/dL, erythrocyte sedimentation rate (ESR) 150 mm/h, C-reactive protein (CRP) 50 mg/dL; rheumatoid factor and antinuclear antibody test are negative. Because of family history, genetic testing was performed and revealed positivity for the HLA-B27 gene.