UMEM Educational Pearls

Category: Toxicology

Title: Spider bite

Keywords: Brown Recluse,envenomation,spider,loxoscelism (PubMed Search)

Posted: 3/3/2011 by Ellen Lemkin, MD, PharmD
Click here to contact Ellen Lemkin, MD, PharmD


Recently a case report was published in which a child was incorrectly diagnosed with MRSA. He actually had systemic loxoscelism from a Brown Recluse spider bite.

A patient who has been bitten by brown recluse spider bite may present with pruritis, pain and swelling. The classic lesion has a bluish-purple central region, surrounded by concentric rings of pale ischemia and erythema. (“red, white and blue”) Bites may progress over days to a bleb with necrosis and eschar formation, followed by ulceration.

Systemic loxoscelism presents with a scarlatiniform rash that spreads dependently. It may have the classic purple lesion surrounded by concentric rings of pale ischemia and erythema. The patient may be uncomfortable but is usually stable. Treatment is supportive care.


Rogers, KM, Klotz CR, Jack M, Seger D. Systemic Loxoscelism in the Age of Community-Acquired Methicillin-Resistant Staphylococcus aureus. Ann of EM Feb 2011 57(2); 138-40.