II. Types: Recluse Spider scientific names

  1. Loxosceles arizonica
  2. Loxosceles deserta
  3. Loxosceles devia
  4. Loxosceles laeta
  5. Loxosceles rufescens
  6. Loxosceles reclusa

III. Epidemiology

  1. Spiders are most abundant and active on warm nights
  2. Bites are most common in early morning hours (Brown recluse is nocturnal)
  3. Brown Recluse Spiders distribution
    1. South America
    2. Southern United States (South of I-80)
      1. Southern half of Iowa, Ilinois and Ohio
      2. East through Kentucky, Tennessee and Georgia
      3. West through Kansas, Oklahoma, and Texas
  4. Recluse Spiders
    1. Eleven Loxosceles Spider species in North America (including Brown Recluse or Loxosceles reclusa)
    2. Other Recluse Spiders worldwide
      1. Siz-Eyed Sand Spider
        1. Southern African Spider (related to Brown Recluse Spider)
      2. Chilean Recluse Spider (arana de rincon, aranha-marrom, corner Spider)
        1. Most dangerous of the Recluse Spiders

IV. Mechanism

  1. Autoimmune response from cytokines, Neutrophil activation and Lymphocytes
  2. Venom induced cytotoxicity
    1. Contains phospholipase enzyme (Sphingomyelinase D)
    2. Results in local and sometimes systemic reaction

V. Pathophysiology

  1. Brown Recluse Spider identification
    1. Males are non-descript brown Spiders
    2. Three pair of eyes in dyads (one pair anterior, and the other 2 pairs are lateral to either side)
      1. Most Spiders have 4 pair of eyes in 2 rows
    3. Females are more distinctive
      1. Thin torso
      2. Larger leg spans (20 to 30 mm)
      3. Darker brown on the dorsal body
      4. Dorsal pattern on thorax resembles a fiddle (or inverted violin)
        1. Not visible in young Spiders, and faded in older Spiders
  2. Circumstances
    1. Spiders hide indoors in dark areas (e.g. piles of clothing, behind furniture)
    2. Bed linens or bedclothes squeeze Spider against skin
    3. Most common bite sites
      1. Axilla
      2. Waist
      3. Foot and ankles (under socks)

VI. Signs: Local bite site (cutaneous Loxoscelism)

  1. Hours 1-3
    1. Minimally painful bite initially
  2. Hours 3-12
    1. Tender, red, violaceous or hemorrhagic halo forms around bite site
  3. Hours 12-24
    1. Painful wound site edema
    2. Wound site erythema may become irregular and localized bullae may develop
  4. Hours 72+
    1. Central necrosis (40% of cases, Necrotic Arachnidism)
  5. Days 5 to 7
    1. Dry necrotic eschar forms
  6. Weeks 2 to 3
    1. Eschar separates with underlying ulceration
    2. Healing over months, with scarring in 13% of cases

VII. Signs: Systemic reactions

  1. General
    1. Serious systemic reactions are uncommon with Brown Recluse (more common with arana de rincon)
  2. Mild Hemolysis
    1. Mild Hemolysis
    2. Mild coagulopathy
  3. Severe Hemolysis (Viscerocutaneous Loxoscelism)
    1. Severe intravascular hemolytic syndrome
    2. Fever to 39-40 degrees Celsius
    3. Chills, Vomiting, and Joint Pain
    4. Hematuria
    5. Petechiae
    6. Measles-like toxic erythema rash

VIII. Differential Diagnosis

  1. General
    1. Brown Recluse Spider Bites are overdiagnosed
    2. Consider other causes of necrotic wounds (unless living in regions where Brown Recluse Spider Bites are common)
    3. Vetter (2002) Ann Emerg Med 39:544-6 [PubMed]
  2. Cellulitis
  3. Skin Abscess
  4. Diabetic Ulcer
  5. Syphilis
  6. Skin cancer
  7. Pyoderma Gangrenosum
  8. Lyme Disease
  9. Erythema Migrans
  10. Cutaneous Anthrax

IX. Diagnosis: Findings suggestive of alternative diagnosis (Mnemonic: NOT RECLUSE)

  1. Numerous bite lesions
  2. Occurrence with non-classic trigger for recluse bite (e.g. gardening)
  3. Timing outside typical North American Recluse bite window (April to October)
  4. Red Center (instead of the typical pale, blue-white or purple center of a Recluse bite)
  5. Elevated (instead of the typical flat or sunken appearance of a recluse bite)
  6. Chronic Wound >3 months old
  7. Large wound diameter (>10 cm)
  8. Ulcerates too early (<7 days)
  9. Swelling ouside face and feet
  10. Exudative or pustular (unlike the dry Recluse bite wounds)
  11. Stoecker (2017) JAMA Dermatol 153(5): 377-8 [PubMed]

XI. Management

  1. Initial symptomatic relief
    1. Ice packs to wound (on for 20 min per hour)
      1. Sphingomyelinase toxin is inactivated by cold
      2. Ice prevents further skin injury (including necrosis)
    2. Analgesics
    3. Elevate extremity with bite site
    4. Antihistamines
  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
    5. Consider referral to plastic surgery for wound check on follow-up
  3. Specific Local Therapies
    1. No specific therapy has been shown to be beneficial
    2. Antitoxin is not available outside of South America (esp. Brazil)
    3. Avoid ineffective or unsupported treatments
      1. Avoid Leukocyte inhibitors (Colchicine)
      2. Avoid hyperbaric oxygen (no evidence to support as of 2017)
      3. Dapsone use is controversial
        1. May considered in severe cases (e.g. Chilean Recluse Spider)
        2. Dose: 50-100 mg twice daily for 10 days
        3. Postulated to decrease Neutrophil degranulation and necrosis
        4. Do not use if G6PD positive (due to Hemolytic Anemia risk; test first)
    4. 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

XII. Course

  1. Anticipate healing over 1-8 weeks
  2. Major scarring at wound site occurs in 10-15% of cases

XIII. Prevention

  1. Shake clothes out before putting on

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Ontology: brown recluse spider bite (C0241820)

Concepts Injury or Poisoning (T037)
English bites brown recluse spider, brown recluse spider bite, bite brown recluse spider, spider bite brown recluse, Brown Recluse Spider Bites

Ontology: Genus Loxosceles (C0323753)

Concepts Eukaryote (T204)
SnomedCT 75179008, 106861008
English Loxosceles, Loxosceles (organism), Genus Loxosceles (organism), Genus Loxosceles, loxosceles, Genus: Loxosceles, Skin necrosis spider, Loxosceles, NOS
Spanish género Loxosceles (organismo), género Loxosceles, Loxosceles (organismo), Loxosceles

Ontology: Brown Recluse Spider (C0323754)

Definition (MSH) A spider of the genus Loxosceles, found in the midwestern and other parts of the United States, which carries a hemolytic venom that produces local necrosis or ulceration.
Concepts Eukaryote (T204)
MSH D063287
SnomedCT 23312003
English Loxosceles reclusa Gertsch & Mulaik, 1940, brown recluse spider, recluse brown spider, spider brown recluse, brown recluse spiders, brown spiders, loxoceles reclusa, brown spider, Recluse Spider, Brown, Recluse Spiders, Brown, Spiders, Brown Recluse, Spiders, Brown Violin, Violin Spiders, Brown Violin Spiders, Violin Spider, Brown Recluse Spiders, Spider, Brown Violin, Violin Spider, Brown, Spider, Violin, Spiders, Violin, Spider, Brown Recluse, Loxosceles reclusa, Violin Spiders, Brown, Brown Violin Spider, Brown Recluse Spider, Brown recluse spider, Loxosceles reclusus, Violin spider, Loxosceles reclusus (organism)
Czech Loxosceles reclusa, koutník jedovatý
French Araignée violon, Recluse brune, Araignée violoniste, Araignée recluse brune, Loxosceles reclusa
German Loxosceles reclusa, Violinenspinne, Amerikanische Braunspinne, Einsiedlerspinne
Italian Ragno eremita marrone
Spanish Araña Reclusa Parda, Loxosceles reclusus (organismo), araña de violín, pardo recluse araña, Loxosceles reclusus
Polish Pustelnik brunatny
Russian КОРИЧНЕВЫЙ ПАУК-ОТШЕЛЬНИК, ПАУК-ОТШЕЛЬНИК КОРИЧНЕВЫЙ, PAUK-OTSHEL'NIK KORICHNEVYI, ПАУК-СКРИПАЧ, KORICHNEVYI PAUK-OTSHEL'NIK, PAUK-SKRIPACH
Portuguese Aranha Marrom Reclusa

Ontology: Poisoning due to brown recluse spider venom (C2711013)

Concepts Injury or Poisoning (T037)
SnomedCT 40119006, 217667008
English Poisoning due to brown spider venom, Poisoning-brown spider venom, Poisoning by brown recluse spider bite, Poisoning due to brown recluse spider venom (disorder), Poisoning by brown recluse spider bite (disorder), Poisoning due to brown recluse spider venom, Poisoning due to brown spider venom (disorder), Poisoning by Loxosceles bite, Poisoning due to brown spider venom (finding)
Spanish envenenamiento por picadura de araña marrón (hallazgo), envenenamiento por veneno de araña reclusa parda (trastorno), envenenamiento por veneno de araña reclusa parda, envenenamiento por picadura de la araña de los cuadros (trastorno), envenenamiento por picadura de la araña de los cuadros, envenenamiento por picadura de araña marrón, envenenamiento por picadura de araña marrón (trastorno), envenenamiento por picadura de Loxosceles