Brown recluse spider bite

Background

Brown recluse range (yellow area)

Brown recluse

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)

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

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

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