Emergency Medicine Book

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Brown Recluse SpiderAka: Recluse Spider, Fiddleback Spider, Loxosceles reclusa, Loxoscelism, Loxosceles Spider

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  1. See Also
    1. Insect Bite
  2. Types: Recluse spider scientific names
    1. Loxosceles arizonica
    2. Loxosceles deserta
    3. Loxosceles devia
    4. Loxosceles laeta
    5. Loxosceles rufescens
    6. Loxosceles reclusa
  3. Epidemiology
    1. Spiders are most abundant and active on warm nights
    2. Bites are most common in early morning hours
  4. Mechanism
    1. Autoimmune response from cytokines and Lymphocytes
    2. Venom induced cytotoxicity
      1. Contains phospholipase enzyme (Sphingomyelinase D)
      2. Results in local and sometimes systemic reaction
  5. Pathophysiology
    1. Brown recluse spider identification
      1. Males are non-descript brown spiders
      2. Females are more distinctive
        1. Larger leg spans (20 to 30 mm)
        2. Darker brown on the dorsal body
        3. Dorsal pattern resembles a fiddle
    2. Circumstances
      1. Bed linens or bedclothes squeeze spider against skin
      2. Most common bite sites
        1. Axilla
        2. Waist
        3. Foot and ankles (under socks)
  6. Signs: Local bite site (loxoscelism)
    1. Discoloration
      1. Hemorrhagic
      2. Erythematous
      3. Violaceous
    2. Central necrosis
  7. Signs: Systemic reactions
    1. Mild Hemolysis
      1. Mild Hemolysis
      2. Mild coagulopathy
    2. Severe Hemolysis
      1. Viscerocutaneous loxoscelism
      2. Severe intravascular hemolytic syndrome
      3. Fever to 39-40 degrees Celsius
      4. Chills, Vomiting, and joint pain
      5. Hematuria
      6. Petechiae
  8. Differential Diagnosis
    1. Brown recluse Spider Bites are overdiagnosed
      1. Consider other causes of necrotic wounds
      2. Vetter (2002) Ann Emerg Med 39:544
  9. Labs
    1. Complete Blood Count and Peripheral Smear
      1. Hemolytic Anemia
      2. Thrombocytopenia
    2. ProTime (PT)
    3. Partial Thromboplastin Time (PTT)
  10. Management
    1. Initial symptomatic relief
      1. Ice packs
      2. Analgesics
      3. Elevate extremity with bite site
    2. Additional wound care measures
      1. Basic wound care and cleansing of site
      2. Debride necrotic tissue
      3. Antibiotics if signs of Cellulitis
        1. Consider wound culture
      4. Tetanus prophylaxis
    3. Specific Local Therapies
      1. No specific therapy has been shown to be beneficial
      2. Avoid ineffective or unsupported treatments
        1. Avoid Leukocyte inhibitors (Dapsone, Colchicine)
        2. Avoid hyperbaric oxygen
      3. Avoid early local procedures (spreads necrosis)
        1. Avoid early local Corticosteroid Injection
        2. Avoid early lesion excision
          1. Consider later with grafting if scarring present
    4. Severe hemolytic systemic reaction
      1. Systemic Corticosteroids
      2. Organ specific supportive therapies
  11. Course
    1. Anticipate healing over 1-8 weeks
    2. Major scarring at wound site occurs in 10-15% of cases
  12. References
    1. Cacy (1999) J Fam Pract 48(7):536
    2. Diaz (2007) Am Fam Physician 75(6):869
    3. Swanson (2005) N Engl J Med 352:700

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