Diferencia entre revisiones de «Brown recluse spider bite»
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===Mechanism=== | ===Mechanism=== | ||
*Venom contains variety of cytotoxic enzymes, principally Hyaluronidase and Sphingomyelinase-D, which cause a necrotic wound | *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 | **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) | **Sphingomyelinase-D: causes necrosis and lesion formation by initiating the release of pro-inflammatory mediators (thromboxanes, leukotrienes, prostaglandins, and neutrophils) | ||
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==Diagnosis== | ==Diagnosis== | ||
*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 | ||
**May be remarkable for hemolysis, hemoglobinuria, and hematuria | **May be remarkable for hemolysis, hemoglobinuria, and hematuria | ||
**Coagulopathy may be present (elevated fibrin split products, decreased fibrinogen concentrations, and a positive [[D-dimer]]) | **Coagulopathy may be present (elevated fibrin split products, decreased fibrinogen concentrations, and a positive [[D-dimer]]) | ||
**Increased PT and PTT | **Increased PT and PTT | ||
==Management== | ==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 als methemoglobinemia | |||
==Disposition== | ==Disposition== | ||
*Typically d/c home | |||
==See Also== | ==See Also== | ||
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==External Links== | ==External Links== | ||
== | ==References== | ||
<references/> | <references/> | ||
[[Category:Environ]] | [[Category:Environ]] | ||
[[Category:Derm]] | [[Category:Derm]] | ||
Revisión del 17:44 6 mar 2016
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 w/ 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 w/ 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
- Hymenoptera stings (bees, wasps, ants)
- Mammalian bites
- Closed fist infection (Fight bite)
- Dog bite
- Marine toxins and envenomations
- Toxins (ciguatera, neurotoxic shellfish poisoning, paralytic shellfish poisoning, scombroid, tetrodotoxin
- Stingers (stingray injury)
- Venomous fish (catfish, zebrafish, scorpion fish, stonefish, cone shells, lionfish, sea urchins)
- Nematocysts (coral reef, fire coral, box jellyfish, sea wasp, portuguese man-of-war, sea anemones)
- Phylum porifera (sponges)
- Bites (alligator/crocodile, octopus, shark)
- Scorpion envenomation
- Reptile envenomation
- Spider bites
Diagnosis
- 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 als methemoglobinemia
Disposition
- Typically d/c home