Question

Which of the following diseases is associated with the HLA B 27 subtype?

• A. Addison's disease
• B. Myasthenia gravis
• C. Reiter's syndrome
• D. Psoriasis

Hint:

Think of the seronegative spondyloarthropathy with a triad of arthritis, conjunctivitis and urethritis.

Answer 1

The Correct Option is C

Step 1: Understanding the Question.
We need to pick the disease from the list that is strongly linked to the HLA B27 gene marker.

Step 2: Key Concept.
HLA B27 is a human leukocyte antigen marker that shows the strongest known association with a group of joint diseases called the seronegative spondyloarthropathies. This group includes ankylosing spondylitis, reactive arthritis (Reiter's syndrome), the joint form of psoriatic arthritis, and enteropathic arthritis linked to inflammatory bowel disease. Among these, ankylosing spondylitis and reactive arthritis show the tightest link to HLA B27.

Step 3: Match Reiter's syndrome to HLA B27.
Reiter's syndrome, now usually called reactive arthritis, is a classic triad of arthritis, conjunctivitis (or uveitis) and urethritis that follows a gut or genital infection. It has one of the strongest HLA B27 associations of any disease, often quoted as present in most patients with this condition.

Step 4: Why the other options are wrong.
Addison's disease, primary adrenal insufficiency, is mainly an autoimmune disease of the adrenal cortex and is not linked to HLA B27. Myasthenia gravis is an autoimmune disease of the neuromuscular junction, linked more to HLA DR3 and thymus abnormalities, not HLA B27. Psoriasis itself, the skin disease alone, has its own separate HLA associations (such as HLA Cw6), and it is specifically psoriatic arthritis, not plain skin psoriasis, that carries some HLA B27 link, and even that link is weaker than in Reiter's syndrome.

Step 5: Final Answer.
The disease most associated with HLA B27 here is
\[ \boxed{\text{Reiter's syndrome (reactive arthritis)}} \]