Question

HLA-B27 is usually detected in all of the following conditions EXCEPT

• A. Systemic lupus erythematosus
• B. Ankylosing spondylitis
• C. Psoriatic arthritis
• D. Reactive arthritis

Hint:

Three of the four options belong to the same family of seronegative joint diseases — one does not.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question wants the one condition among the four that is NOT associated with the HLA-B27 haplotype.

Step 2: Key Concept or Approach:
HLA-B27 is the defining genetic marker of the seronegative spondyloarthropathies — a group of joint diseases that are rheumatoid-factor negative and share axial and enthesitis-related inflammation. This group includes ankylosing spondylitis, reactive arthritis (Reiter's syndrome), psoriatic arthritis, and enteropathic arthritis linked to inflammatory bowel disease. Systemic lupus erythematosus belongs to a completely different family of disease — a connective tissue disorder driven by autoantibodies (ANA, anti-dsDNA) and immune complex deposition, and its genetic associations are with HLA-DR2 and HLA-DR3, not HLA-B27.

Step 3: Working Through the Options:
Systemic lupus erythematosus is the exception because it is an autoantibody-mediated disease with no established HLA-B27 link. Ankylosing spondylitis shows the strongest HLA-B27 association of any rheumatic disease. Psoriatic arthritis, particularly its axial and enthesitis-related pattern, is HLA-B27 associated. Reactive arthritis, classically triggered by a preceding GI or genitourinary infection, is also strongly linked to HLA-B27.

Step 4: Conclusion:
The correct answer is Systemic lupus erythematosus.