The brown recluse (Loxosceles reclusa)is the last one I wanted to cover before BUG WEEK 2007 ended. Actually, there will probably be another bug week... or maybe just a worm week... or half week (I don't think I could do a full week of worms).
The brown recluse is interesting to me for a couple reasons. The first is that it has a painless bite. The second is that it is in Texas (like me).
As the name implies, the spider is both brown and reclusive. It lives in wood sheds, garages, attics, etc. Basically any place where it can be left alone. We come across them when we decide to clean up these places. It's back is supposed to look like a violin, which it does sometimes. It is found in the midwest and the Gulf of Mexico states (except Florida).
It has skin findings! (sometimes) Most bites are relatively mild and could cause some inflammation, which should be treated with ice packs. If it starts to turn dusky and the wound is not healing, it might be necrotic. This is rare, but serious. The necrotic (dying) tissue can spread and take a while to heal. In some cases, multi system organ failure can occur. Dapsone has been used with mixed results to decrease necrosis.
Elston DM, Miller SD, Young RJ, Eggers J, McGlasson D, Schmidt WH, Bush A. Comparison of colchicine, dapsone, triamcinolone, and diphenhydramine therapy for the treatment of brown recluse spider envenomation: a double-blind, controlled study in a rabbit model.Arch Dermatol. 2005 May;141(5):595-7.
This study basically said that none of the agents helped with necrosis or eschar formation in the rabbits
These bites are very rare and often overdiagnosed. The following conditions should be kept on your differential diagnosis as they present similarly and are far more common:
1. Staph or Strep infections
2. Pyoderma gangrenosum
3. Herpes
4. Diabetic ulcer
5. Squamous cell carcinoma
6. Deep fungal infections
7. Chemical burns
8. Localized vasculitis
9. Sporotrichosis
10. Site of tick bite in Lyme disease
I actually saw a patient with a lesion that could be any one of these things today. Brown recluse bite was not in the top 10 of our differential.
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