Review Question - QID 109539

This patient is a young male presenting with back pain that improves upon activity and decreased mobility suggesting a diagnosis of ankylosing spondylitis (AS). The best initial step in management of AS is radiography of the lumbosacral spine to look for sacroiliitis.

Ankylosing spondylitis classically presents in a young male who complains of back pain that improves with activity. Patients may experience other complications including uveitis, aortitis, and restrictive lung disease. The best initial step in management is a radiograph of the lumbosacral spine to look for signs of sacroiliitis which is typically the first radiographical finding. The most accurate test is an MRI of the sacroiliac joint.

Illustration A is an MRI demonstrating sacroiliitis. This is a T1-weighted image before and after contrast injection with the arrow identifying inflammation at the SI joint.

Incorrect Answers:
Answer 1: Pulmonary function tests could be used to diagnose restrictive lung disease which this patient may be experiencing given his shortness of breath. Restrictive lung disease is a known complication of AS; however, the best initial step in management is a radiograph of the lumbosacral spine to diagnose AS.

Answer 3: MRI of the sacroiliac joint is the most accurate diagnostic test of AS. It would not be performed as the initial test.

Answer 4: CT scan of the chest would be useful for assessing the lungs and rib cage for any cause of this patient's shortness of breath; however, it would not be the best initial test.

Answer 5: Ultrasound could be an appropriate initial diagnostic test for a tension pneumothorax or to assess for an abdominal aortic aneurysm; however, it would not be appropriate in assessing AS.

Bullet Summary:
Ankylosing spondylitis presents with back pain that is worse in the morning and improves with activity, and the best initial test is a radiograph of the lumbosacral spine.