Case 27

Published on 18/02/2015 by admin

Filed under Allergy and Immunology

Last modified 18/02/2015

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CASE 27

Arnold, a 28-year-old man, recently returned from a camping trip in Massachusetts and has noticed several large, itchy, erythematous (red) patches (that seem to “move around”) on his arms. He remembers being bitten by some “bugs” while camping, but otherwise there is no significant medical history of note and no drug history. You recall reading about Lyme disease while you were at medical school and order a serum test for antibodies to Borrelia burgdorferi. The test comes back positive, confirming your suspicions (and the recognition of a classic “erythema migrans” picture).

You treat Arnold with a 28-day course of doxycycline with complete resolution of the symptoms. Several months later, Arnold reappears in your office with severe arthritic symptoms of several weeks’ duration, predominantly in the large joints (knees). He has been taking over-the-counter anti-inflammatory medication with no relief. An aunt suffers from rheumatoid arthritis, and he is concerned that he is developing the same disease.

You are concerned instead that this represents a persistent manifestation of the Lyme disease. In fact, titers to B. burgdorferi are even higher than when you first saw him. Despite further rounds of antibiotic therapy there is no obvious resolution of the arthritic picture, and indeed over the next 3 years his disease is marked by frequent exacerbations. What are some current thoughts regarding this picture? What is known about the pathophysiology?

QUESTIONS FOR GROUP DISCUSSION

1. Review the mode of infection with Borrelia burgdorferi.
2. Describe the tests used to diagnose infection with B. burgdorferi. What is the confirmation test in North America?
3. Review the inflammatory process (see Case 23). What evidence is there that B. burgdorferi synovitis is the result of antigen-driven activation?
4. Spirochete survival has been used to explain persistent synovitis. Discuss.
5. Discuss how molecular mimicry could lead to an autoimmune basis for persistent synovitis.
6. Explain dominant antigenic epitope and how this could account for the fact that resident Lyme disease is rare in Europe.
7. Discuss various forms of therapy and the rationale for each.

RECOMMENDED APPROACH

Implications/Analysis of Family History

A major genetic risk factor for therapy failure in patients with Lyme disease is HLA-DR4. Interestingly, Arnold’s aunt has rheumatoid arthritis, which is not linked to Lyme disease, but about 70% of patients with RA express the HLA-DR4 allele (control, 28%).

Implications/Analysis of Clinical History

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