Spider Bite, Brown Recluse



Local or systemic illness caused by brown recluse spider bite envenomation


  • Brown recluse spider (also known as the fiddleback spider) features:
    • Appearance:
      • Delicate body and legs spanning 10–25 mm
      • Tan- to dark-brown with darker violin-shaped marking visible on the upper aspect of the head
      • 3 pairs of eyes
    • Found widely throughout the south-central part of the U.S.
    • Habitat: Typically warm and dry locations, indoors or outdoors such as wood piles, bundles of rags, cellars, under rocks, or in attics
    • Bites are typically defensive
  • Mechanism of toxicity:
    • Venom is a complex cocktail of enzymes and peptides that:
      • Binds to RBC and causes hemolysis
      • Causes prostaglandin release and activates complement cascade
      • Causes lipolysis and tissue necrosis
      • Triggers platelet aggregation and thrombosis
      • Triggers allergic response to venom antigenic properties
      • May lead to shock and DIC in rare cases
    • Toxicity proportional to:
      • The amount of venom relative to the size of patient
      • Location of envenomation on the body

Pediatric Considerations
  • Children are more vulnerable to a given amount of venom than healthy adults
  • Fatality more common in children due to severe intravascular hemolysis

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