Brown recluse spider bite: Difference between revisions

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*Brown violin shape on cephalothorax (fiddleback)
*Brown violin shape on cephalothorax (fiddleback)
*In Southern midwestern US
*In Southern midwestern US
* ''Loxosceles'' family
*''Loxosceles'' family


===Mechanism===
===Mechanism===
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==Clinical Features==
==Clinical Features==
*Bite is initially painless
*Bite is initially painless
*Mild reaction
*Mild reaction (most common)
**Most common
**Mild erythematous lesion that later becomes firm and heals without scar
**Mild erythematous lesion that later becomes firm and heals without scar
*Severe reaction
*Severe reaction
**Begins w/ mild-severe pain several hrs after bite accompanied by erythema and swelling  
**Begins with mild-severe pain several hrs after bite accompanied by erythema and swelling  
**Hemorrhagic blister then forms surrounded by vasoconstriction-induced blanched skin
**Hemorrhagic blister then forms surrounded by vasoconstriction-induced blanched skin
**By day 3 or 4 hemorrhagic area may become ecchymotic
**By day 3 or 4 hemorrhagic area may become ecchymotic
***Leads to "red, white, and blue" sign (erythema, blanching, ecchymosis)
***Leads to "red, white, and blue" sign (erythema, blanching, ecchymosis)
**By end of first week ecchymotic area may become necrotic w/ eschar formation
**By end of first week ecchymotic area may become necrotic with eschar formation
*Systemic effects
*Systemic effects (rare)
**Rare
**Occur predominantly in children 24-72hr after the bite
**Occur predominantly in children 24-72hr after the bite
***Include nausea/vomiting, fever, arthralgias, DIC, rhabdo, renal failure
**Include nausea/vomiting, fever, arthralgias, DIC, rhabdo, renal failure


==Differential Diagnosis==
==Differential Diagnosis==
{{Bites and stings DDX}}
{{Bites and stings DDX}}


==Diagnosis==
==Evaluation==
*Definitive diagnosis is achieved only when the biting spider is positively identified
*Definitive diagnosis is achieved only when the biting spider is positively identified
*Labs
*Labs
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*Local wound care and tetanus prophylaxis
*Local wound care and tetanus prophylaxis
*[[Antibiotics]] are indicated only if signs of infection exist; secondary infections are uncommon
*[[Antibiotics]] are indicated only if signs of infection exist; secondary infections are uncommon
*Although some texts recommend Dapsone, it has been shown to be of limited benefit and is associated with hemolysis in G6PD patients and als methemoglobinemia
*Although some texts recommend Dapsone, it has been shown to be of limited benefit and is associated with hemolysis (in G6PD patients) and [[methemoglobinemia]]


==Disposition==
==Disposition==
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==See Also==
==See Also==
*[[Bites and Stings]]
*[[Envenomations, bites and stings]]


==External Links==
==External Links==

Revision as of 04:13, 1 January 2017

Background

Brown recluse range (yellow area)
Brown recluse
  • Brown violin shape on cephalothorax (fiddleback)
  • In Southern midwestern US
  • Loxosceles family

Mechanism

  • Venom contains variety of cytotoxic enzymes, principally Hyaluronidase and Sphingomyelinase-D, which cause a necrotic wound
    • Hyaluronidase: facilitates the penetration of the venom into tissue but does not induce lesion development
    • Sphingomyelinase-D: causes necrosis and lesion formation by initiating the release of pro-inflammatory mediators (thromboxanes, leukotrienes, prostaglandins, and neutrophils)

Clinical Features

  • Bite is initially painless
  • Mild reaction (most common)
    • Mild erythematous lesion that later becomes firm and heals without scar
  • Severe reaction
    • Begins with mild-severe pain several hrs after bite accompanied by erythema and swelling
    • Hemorrhagic blister then forms surrounded by vasoconstriction-induced blanched skin
    • By day 3 or 4 hemorrhagic area may become ecchymotic
      • Leads to "red, white, and blue" sign (erythema, blanching, ecchymosis)
    • By end of first week ecchymotic area may become necrotic with eschar formation
  • Systemic effects (rare)
    • Occur predominantly in children 24-72hr after the bite
    • Include nausea/vomiting, fever, arthralgias, DIC, rhabdo, renal failure

Differential Diagnosis

Envenomations, bites and stings

Evaluation

  • Definitive diagnosis is achieved only when the biting spider is positively identified
  • Labs
    • May be remarkable for hemolysis, hemoglobinuria, and hematuria
    • Coagulopathy may be present (elevated fibrin split products, decreased fibrinogen concentrations, and a positive D-dimer)
    • Increased PT and PTT

Management

  • Local wound care and tetanus prophylaxis
  • Antibiotics are indicated only if signs of infection exist; secondary infections are uncommon
  • Although some texts recommend Dapsone, it has been shown to be of limited benefit and is associated with hemolysis (in G6PD patients) and methemoglobinemia

Disposition

  • Typically discharge home

See Also

External Links

References