A 28-year-old man presents to the clinic with a 6-month history of dull, aching pain in his lower back and buttocks. He states the pain is worst in the morning, lasting for about two hours, and improves significantly after he goes for his morning run. He denies any specific trauma but notes that the stiffness has been progressively worsening, occasionally waking him up in the middle of the night. Past medical history is negative. Vital signs are within normal limits. On physical examination, there is limited forward flexion of the lumbar spine and tenderness over the sacroiliac joints. A radiograph of the pelvis shows subchondral sclerosis and erosions at the sacroiliac joints.
Which of the following is the most likely additional finding in this patient?
The correct answer is:
A) Aortic regurgitation
This patient’s presentation of a young male with chronic inflammatory back pain that improves with exercise and is worse with rest, along with radiographic evidence of sacroiliitis, is highly suggestive of ankylosing spondylitis (AS). AS is a chronic inflammatory disease of the axial skeleton. Extra-axial manifestations are common and frequently tested. Aortic regurgitation occurs due to inflammation of the aortic root and valve cusps (aortitis), which can lead to aortic root dilation. Other common extra-axial manifestations include uveitis (not episcleritis), apical pulmonary fibrosis, and restrictive lung disease.
Answer choice B: Episcleritis, is incorrect. While AS is strongly associated with eye inflammation, the classic association is acute anterior uveitis (iritis), which presents with a painful, red eye and photophobia. Episcleritis is more commonly associated with rheumatoid arthritis or inflammatory bowel disease.
Answer choice C: Increased chest expansion, is incorrect. AS leads to decreased chest expansion due to involvement of the costovertebral and costosternal joints. Monitoring chest expansion is a common way to track disease progression.
Answer choice D: Presence of rheumatoid factor, is incorrect. AS belongs to the group of seronegative spondyloarthropathies, meaning patients are typically negative for rheumatoid factor (RF) and antinuclear antibodies (ANA). They are, however, strongly associated with the HLA-B27 allele.
Answer choice E: Symmetric small joint arthritis, is incorrect. This is the hallmark of rheumatoid arthritis. AS typically involves the axial skeleton and may involve large peripheral joints, like the hips or shoulders, asymmetrically, but it does not typically present with the symmetric small joint involvement of the hands and feet.
Key Learning Point
Ankylosing Spondylitis is an inflammatory arthritis characterized by sacroiliitis and bamboo spine. Beyond the skeleton, it is associated with the A's: Acute anterior uveitis, Aortic regurgitation, Apical fibrotic lung disease, and Achilles tendon enthesitis.
