A 45-year-old man presents with chronic inflammatory low back pain for 3 years, worse in the morning with improvement with exercise and no relief with rest. X-ray of the sacroiliac joints shows bilateral erosions and sclerosis. MRI demonstrates bone marrow edema of the sacroiliac joints. Which HLA allele is most strongly associated with this condition?
- A HLA-DR4
- B HLA-DQ2
- C HLA-B27 ✓
- D HLA-DR3
Correct answer: C. HLA-B27
Explanation
The clinical picture is classic ankylosing spondylitis, which is strongly associated with HLA-C27 (present in approximately 90% of patients). HLA-DR4 is associated with rheumatoid arthritis, HLA-DQ2 with celiac disease, and HLA-DR3 with autoimmune conditions such as SLE and type 1 diabetes. HLA-C27 testing is part of the diagnostic workup for axial spondyloarthritis.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.