A 26-year-old male presents with chronic lower back pain that improves with exercise and worsens with rest, accompanied by morning stiffness. What genetic marker is positive in 90% of cases?
Answer and explanation
Correct answer: C. HLA-B27
- Step 1: Inflammatory back pain with morning stiffness and bilateral sacroiliitis in a young male indicates ankylosing spondylitis.
- Step 2: Ankylosing spondylitis has the strongest genetic association among the seronegative spondyloarthropathies, with over 90% of affected patients testing positive for the major histocompatibility complex allele HLA-B27.
Answer
HLA-B27.
Why not the others: HLA-DR4 is strongly associated with rheumatoid arthritis. HLA-DQ2 (and DQ8) is associated with celiac disease. HLA-B51 is associated with Behçet disease.
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