USMLE Step 1 Question 342

Question:

A 22-year-old male presents with complaints of photophobia, dysuria and arthralgias. Upon further questioning he admits to having had a sexually transmitted disease diagnosed a few weeks ago, which was treated with antibiotics. On physical exam, his eye is erythematous with a watery discharge and his left knee is swollen, warm and tender. What is the most likely HLA type found in this patient?

Correct Answer: B.  HLA B27

This patient is experience reactive arthritis (also know as Reiter’s Arthritis) which is a seronegative inflammatory arthritis that often follows a GU infection (like Chlamydia described in the history) or a bacterial GI infection. This group of seronegative inflammatory arthritides are associated with HLA B27. Also in this group are psoriasis, ankylosing spondylitis and IBD.

HLA B8 is assoicated with Graves’ disease and celiac sprue.

HLA DR2 is associated with multiple sclerosis, SLE and Goodpasture’s syndrome.

HLA DR3 is associated with diabetes type I (especially in conjunction with HLA DR4).

HLA DR5 is associated with pernicious anemia, and Hashimoto’s thyroiditis.