Skin nontumor
Infestations
Brown recluse spider

Authors: Priya Nagarajan, M.D., Ph.D., Liye Suo, M.D. (see Authors page)
Editorial Board Member Review: Sara Shalin, M.D., Ph.D.

Revised: 24 July 2017, last major update July 2017

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed Search: Brown recluse spider[title]
Cite this page: Brown recluse spider. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skinnontumorbrownreclusespider.html. Accessed September 26th, 2017.
Definition / general
Essential features
  • Bite and venom can cause extensive necrosis, hemorrhage, blistering and ulceration
  • Misdiagnosis of methicillin resistant Staphylococcus aureus (MRSA) as spider bites has been reported and may have fatal consequences
  • No standard treatment to date
  • Usually associated with eosinophils, but other histologic features vary: neutrophilic vasculitis with hemorrhage, arterial wall necrosis or eschar covered ulceration and subcutaneous necrosis
Terminology
  • Also called loxoscelism (Loxosceles reclusa), necrotizing arachnidism
Epidemiology
  • Mainly populates the southern central states and some South American countries
  • In 2011, 1487 Loxosceles bites were reported in the US, mainly in Southeastern states (Clin Toxicol (Phila) 2012;50:911)
Sites
  • Any body site can be affected, especially exposed skin
  • Cutaneous manifestations occur in around 80% cases around the site of bite, predominantly in the lower limbs (Rev Inst Med Trop Sao Paulo 1989;31:403)
Etiology
  • Bite induced injury
  • Hemotoxic and proinflammatory venom
Clinical features
  • Initial symptoms include burning stinging, pain, erythema and edema
  • Local envenomation associated skin lesions: extensive necrosis, hemorrhage, blistering and ulceration (Semin Cutan Med Surg 2014;33:123)
  • May take 2 months to heal (N Engl J Med 2013;369:e6)
  • Secondary bacterial infections and osteomyelitis have also been reported (Eplasty 2008;8:e45)
  • A chronic pyoderma gangrenosum-like reaction has also been reported (South Med J 1990;83:243)
  • Systemic loxoscelism is a rare complication after envenomation (J Clin Immunol 2014;34:544)
    • Symptoms include severe hemolysis, acute kidney injury, secondary hemophagocytic lymphohistiocytosis
Diagnosis
  • Misdiagnosis may have fatal consequences, especially misdiagnosis of methicillin resistant Staphylococcus aureus (MRSA) as spider bites (N Engl J Med 2006;355:666)
    • NOT RECLUSE: a mnemonic to avoid misdiagnoses (JAMA Dermatol 2017;153:377)
    • Diagnosis can be made by swabbing the lesion and using a specific enzyme linked immunosorbent assay (ELISA) to detect the venom
Case reports
  • 6 year old boy with massive hemolysis, shock and acute renal failure after loxosceles envenomation (Pediatrics 2014;134:e1464)
  • 10 year old boy developed necrotic rash, secondary hemophagocytic lymphohistiocytosis from a brown recluse spider bite (J Clin Immunol 2014;34:544)
  • 22 year old woman with severe haemolytic anaemia with erythrophagocytosis following the bite of a brown recluse spider (Br J Haematol 2014;167:1)
  • 23 year old man developed dermonecrosis and acute kidney injury following the bite of brown recluse spider (Indian J Nephrol 2014;24:246)
  • 60 year old woman with a necrotic lesion of the left breast (JAAPA 2014;27:32)
  • 63 year old woman with bilaterally decreased vision after a bite from a brown recluse spider (Cutan Ocul Toxicol 2016;35:168)
Treatment
  • No standard treatment to date
  • First aid treatment: wash the bite area with soap and water; apply a cold pad to reduce inflammation; seek professional medical treatment (CDC website - Venomous Spiders)
  • Topical treatment: pain control, anti inflammatory medications; topical antibiotics for secondary bacterial infections; hyperbaric oxygen therapy for nonhealing wounds (Adv Skin Wound Care 2016;29:560)
  • Surgical interventions including debridement of the envenomation site and possibly skin grafting (J Foot Ankle Surg 2014;53:320)
  • Therapeutic plasma exchange for severe systemic loxoscelism associated hemolysis and acute kidney failure (J Med Toxicol 2015;11:364)
Clinical images

Images hosted on other servers:
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The brown recluse

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Dorsal view of the brown recluse spider

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Necrotic rash from
a brown recluse
spider bite
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Brown recluse spider bites

Microscopic (histologic) description
  • Varies from neutrophilic vasculitis with hemorrhage to arterial wall necrosis to eschar covered ulceration and subcutaneous necrosis
  • Usually eosinophils in the inflammatory infiltrate
Differential diagnosis
Board review question #1
    Which description of brown recluse spider bites is FALSE:

  1. Cutaneous manifestations occur in around 80% cases around the site of bite, predominantly in the lower limbs
  2. The gold standard for treatment is antibiotics and debridement
  3. Microscopic features vary from neutrophilic vasculitis with hemorrhage to arterial wall necrosis to eschar covered ulceration and subcutaneous necrosis
  4. Misdiagnosis of methicillin resistant Staphylococcus aureus (MRSA) as spider bites may have fatal consequences
  5. Loxosceles reclusa, the brown recluse spider, is one of two venomous spiders in the North America
Board review answer #1
B. There is no standard treatment for a bite from a brown recluse spider.