Brown recluse spider bite: Difference between revisions
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==Clinical Features== | ==Clinical Features== | ||
[[File:MPX2157 synpic16260.png|thumb|Brown recluse spider bite, day 3.]] | |||
[[File:MPX2157 synpic16261.png|thumb|Brown recluse spider bite, day 4.]] | |||
[[File:MPX2157 synpic16262.png|thumb|Brown recluse spider bite, day 5.]] | |||
[[File:MPX2157 synpic16263.png|thumb|Brown recluse spider bite, day 6.]] | |||
[[File:MPX2157 synpic16264.png|thumb|Brown recluse spider bite, day 9.]] | |||
[[File:MPX2157 synpic16265.png|thumb|Brown recluse spider bite, day 10.]] | |||
*Bite is initially painless | *Bite is initially painless | ||
*Mild reaction (most common) | *Mild reaction (most common) | ||
| Line 36: | Line 42: | ||
*Labs | *Labs | ||
**May be remarkable for [[hemolytic anemia|hemolysis]], hemoglobinuria, and [[hematuria]] | **May be remarkable for [[hemolytic anemia|hemolysis]], hemoglobinuria, and [[hematuria]] | ||
**[[Coagulopathy]] may be present (elevated fibrin split products, decreased | **[[Coagulopathy]] may be present (elevated fibrin split products, decreased fibrinogen concentrations, and a positive [[D-dimer]]) | ||
**Increased PT and PTT | **Increased PT and PTT | ||
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==See Also== | ==See Also== | ||
*[[ | *[[Spider bites]] | ||
==External Links== | ==External Links== | ||
Latest revision as of 13:26, 29 May 2022
Background
- 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 hours 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
- Nausea/vomiting
- Fever, arthralgia
- DIC
- Rhabdo
- Renal failure
Differential Diagnosis
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