Ankylosing spondylitis — SCE Rheumatology MCQ

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EasySpondyloarthropathiesAnkylosing spondylitisSCE Rheumatology

A 33-year-old man reports an 8-year history of low back pain that improves with exercise but not with rest. Examination shows reduced lumbar flexion and reduced chest expansion. A pelvic radiograph demonstrates bilateral grade 3 sacroiliitis. What is the most likely diagnosis?

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Correct answer: A — Ankylosing spondylitis

The diagnosis is **ankylosing spondylitis (radiographic axial spondyloarthritis)**. The young age at symptom onset, improvement with exercise rather than rest, reduced lumbar flexion and reduced chest expansion are characteristic clinical features. Most decisively, bilateral grade 3 sacroiliitis meets the modified New York radiographic threshold; NICE specifies bilateral grade 2–4 or unilateral grade 3–4 sacroiliitis for diagnosing ankylosing spondylitis. Osteitis condensans ilii causes iliac-sided sclerosis but does not produce this typical erosive, graded inflammatory sacroiliitis. A lumbar disc prolapse causes mechanical or radicular symptoms rather than bilateral sacroiliitis. Paget disease is unusual at this age, and rheumatoid arthritis does not characteristically cause sacroiliitis.

Reference: National Institute for Health and Care Excellence. NG65: Spondyloarthritis in over 16s: diagnosis and management, recommendation 1.2.5. 2017. https://www.nice.org.uk/guidance/ng65/chapter/Recommendations