AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Background

In the United States, reports of severe envenomations by brown spiders began to appear in the late 1800s, and today, in endemic areas, brown spiders continue to be of significant clinical concern.

Of the 13 species of Loxosceles in the United States, at least 5 have been associated with necrotic arachnidism. Loxosceles reclusus, or the brown recluse spider, is the spider most commonly responsible for this injury.

Dermonecrotic arachnidism refers to the local skin and tissue injury noted with this envenomation. Loxoscelism is the term used to describe the systemic clinical syndrome caused by envenomation from the brown spiders.

Pathophysiology

Brown recluse spider bites can cause significant cutaneous injury with tissue loss and necrosis. Less frequently, more severe reactions develop, including systemic hemolysis, coagulopathy, renal failure, and, rarely, death.

Brown recluse venom, like many of the other brown spider venoms, is cytotoxic and hemolytic. It contains at least 8 components, including enzymes such as hyaluronidase, deoxyribonuclease, ribonuclease, alkaline phosphatase, and lipase. Sphingomyelinase D is thought to be the protein component responsible for most of the tissue destruction and hemolysis caused by brown recluse spider envenomation. The intense inflammatory response mediated by arachidonic acid, prostaglandins, and chemotactic infiltration of neutrophils is amplified further by an intrinsic vascular cascade involving the mediator C-reactive protein and complement activation. These and other factors contribute to the local and systemic reactions of necrotic arachnidism.

Although numerous cases of cutaneous and viscerocutaneous reactions have been attributed to spiders of the genus Loxosceles, confirming the identity of the envenomating arachnid is difficult and rarely accomplished.

Frequency

United States

Although various species of Loxosceles are found throughout the world, L reclusus is found in the United States from the East to the West Coast, with predominance in the south. Recently, reports of persons with "spider bites" presenting to emergency departments have reached near urban legend proportions, prompting many physicians to question the diagnosis of a brown recluse bite in nonendemic areas. The list of conditions that can present in a similar fashion to that of a brown recluse spider envenomation is extensive. A more likely explanation for this epidemic of spider bites is in fact community-acquired methicillin-resistant Staphylococcus aureus (MRSA) skin infections.

Mortality/Morbidity

• Data regarding mortality rates are not reliable because diagnostic tests to detect brown recluse venom in tissue are not readily available.
• Although deaths have been attributed to presumed brown recluse envenomation, severe outcomes are rare. Typical cases involve only local soft tissue destruction.
• In South America, the more potent venom of the species Loxosceles laeta is responsible for several deaths each year.

Age

Systemic involvement, although uncommon, occurs more frequently in children than in adults.

CLINICAL

Section 3 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

History

• The brown recluse spider, living up to its name, is naturally nonaggressive toward humans and prefers to live in undisturbed attics, woodpiles, and storage sheds.
• Brown recluse spiders vary in size and can be up to 2-3 cm in total length. They are most active at night from spring to fall.
• Characteristic violin-shaped markings on their backs have led brown recluse spiders to also be known as fiddleback spiders.
• Envenomation from the brown recluse spider elicits minimal initial sensation and frequently goes unnoticed until several hours later when the pain intensifies.
• An initial stinging sensation is replaced over 6-8 hours by severe pain and pruritus as local vasospasm causes the tissue to become ischemic.
• Symptoms of systemic loxoscelism are not related to the extent of local tissue reaction and include the following:
  
  
  • Morbilliform rash
  • Fever
  • Chills
  • Nausea
  • Vomiting
  • Joint pain
  • Hemolysis
  • Disseminated intravascular coagulation (DIC)
  • Renal failure
  • Seizures
  • Coma

Physical

• Edema around the ischemic bite site produces the appearance of an erythematous halo around the lesion.
  
  
  • The erythematous margin around the site continues to enlarge peripherally, secondary to gravitational spread of the venom into the tissues.
  • Typically, at 24-72 hours, a single clear or hemorrhagic vesicle develops at the site, which later forms a dark eschar (see Media file 1).
• Necrosis is more significant in the fatty areas of the buttocks, thighs, and abdominal wall.

Causes

Dermonecrotic arachnidism has been described in association with several species of Loxosceles spiders, but, in the United States, L reclusus venom is the most potent and the most commonly involved.

DIFFERENTIALS

Section 4 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Other Problems to be Considered

Cutaneous anthrax
Community-acquired MRSA skin infection
Pyoderma gangrenosum

WORKUP

Section 5 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Lab Studies

• Wound cultures and Gram stain may provide valuable information for local wounds.
• If signs of systemic toxicity are present, monitor the patient for evidence of hemolysis, renal failure, and coagulopathy.
• If treatment with dapsone is being considered, obtain a glucose-6-phosphate dehydrogenase (G-6-PD) level before treatment.

Procedures

• Conservative local debridement of necrotic lesions may be performed once the wound margins have been defined. Wide excision is disabling, disfiguring, and seldom indicated.

TREATMENT

Section 6 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Emergency Department Care

• Treatment of brown recluse envenomation is directed by the severity of the injury. General wound management consists of local debridement, elevation, and loose immobilization of the affected area.
• Because the activity of sphingomyelinase D is temperature dependent, application of local cool compresses is helpful and should be continued until progression of the necrotic process appears to have stopped.
• Dapsone, because of its leukocyte inhibiting properties, frequently has been recommended by authorities to treat local lesions. However, because of the potential for adverse effects associated with dapsone use, especially in the setting of G-6-PD deficiency, appropriate caution should be exercised if using this medication. To date, no well-controlled studies have shown dapsone to affect clinical outcome in human brown recluse envenomations; therefore, it is not routinely recommended.
• Other treatments such as colchicine, steroids, antivenom, nitroglycerin patches, and surgical excision have been reported, but insufficient data exist to support their clinical use today.
• Some evidence indicates that hyperbaric oxygen therapy is beneficial in an animal model for reducing skin lesion size, but controlled human studies of this technique have not been performed.
• Patients exhibiting signs of systemic toxicity should be admitted and evaluated for evidence of coagulopathy, hemolysis, hemoglobinuria, renal failure, or further progression of systemic illness.
• Urinalysis can provide early evidence of systemic involvement (eg, hemoglobinuria, myoglobinuria) and can be performed easily at the bedside in all patients.

Consultations

Consult a plastic surgeon or other specialist with experience in wound management in patients who might require delayed skin grafting or have a prolonged recovery period.

MEDICATION

Section 7 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Utilize tetanus prophylaxis, analgesics, and antipruritics as needed. Reserve antibiotics for evidence of true infection and do not administer prophylactically.

Drug Category: Antibiotics

Antibiotics may minimize the local inflammatory component of cutaneous loxoscelism and decrease resulting skin necrosis.

Drug Category: Corticosteroids

These agents have anti-inflammatory properties and cause profound and varied metabolic effects. In addition, these agents modify the body's immune response to diverse stimuli.

Use of corticosteroids is controversial, but some evidence supports their use in systemic loxoscelism because of their RBC membrane–stabilizing effects.

Drug Category: Antihistamines

Antihistamines are used to treat minor allergic reactions and anaphylaxis. Diphenhydramine may be used to pretreat patients with prior documentation of minor allergic reactions. These agents may control itching by blocking effects of endogenously released histamine.

FOLLOW-UP

Section 8 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Further Inpatient Care

• Admit patients to the hospital for observation if they have rapidly expanding lesions or show evidence of systemic toxicity.
• • Patients with rapidly expanding lesions require good conservative wound care, including splinting and elevation. Appropriately treat any bacterial superinfection that occurs.

  • Carefully manage fluid and electrolytes in patients with evidence of systemic loxoscelism. Monitor patients' renal status and provide blood transfusions as needed. A short course of oral prednisone may reduce hemolysis. These patients may be discharged when their renal and hematologic statuses are stable.

Further Outpatient Care

• Before discharging patients from the hospital, instruct them on proper wound care techniques and in proper cooling of the lesion for the first 72 hours. Schedule patients for daily wound checks until the lesion is stable or improving.
• At each follow-up visit for the first 72 hours, perform a urine bedside test for blood and a CBC with platelet count to assess for any evidence of systemic toxicity.
• Inform patients that the development of fever or dark urine necessitates immediate return to the ED or a call to their primary physician.

Deterrence/Prevention

• Persons living in endemic areas should wear protective clothing and remain attentive when venturing into habitats of the brown recluse spider.
• Cobwebs and spiders should carefully be removed from under and behind beds. One should use caution when putting on clothing that has been kept in storage and not worn for some time.

Complications

• Delayed skin grafting may be necessary after 4-6 weeks of standard therapy.
• Losses of digits and amputations have been reported.

Patient Education

• For excellent patient education resources, visit eMedicine's Bites and Stings Center. Also, see eMedicine's patient education articles, Black Widow Spider Bite and Brown Recluse Spider Bite.

MISCELLANEOUS

Section 9 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Medical/Legal Pitfalls

• Failure to warn patients about potential complications
• Failure to arrange follow-up care
• Failure to evaluate the patient for potential complications
• Failure to diagnose brown recluse spider bite
• Failure to consider G-6-PD status before initiation of dapsone therapy

MULTIMEDIA

Section 10 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Media file 1:  Classic finding of a vesicle with surrounding erythema at 24 hours following brown recluse envenomation. Photo by Thomas Arnold, MD.
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Media file 2:  Illustration of a brown recluse spider with the fiddle displayed prominently on its dorsum.
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Media file 3:  Spider envenomations, brown recluse. Envenomation site on inner thigh untreated at 1 week. Photo by Thomas Arnold, MD.
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Media file 4:  Typical appearance of a male brown recluse spider. Photo contributed by Michael Cardwell, Victorville, Calif.
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Media file 5:  Female brown recluse with size scale. Photo contributed by Michael Cardwell, Victorville, Calif.
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Media file 6:  Spider envenomations, brown recluse. Close-up image of dorsal violin-shaped pattern. Photo contributed by Michael Cardwell, Victorville, Calif.
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Media file 7:  Spider bite, brown recluse. Within an hour, the bite area swelled to the size of a quarter. The area turned blue and dark red by the evening of the first day, exceeding the boundaries of a circle drawn around the area of initial swelling by the patient's physician. Courtesy of Dale Losher.
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Media file 8:  Spider bite, brown recluse. The third day after the bite. The skin continues to die. Courtesy of Dale Losher.
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Media file 9:  Spider bite, brown recluse. Another view of the wound 3 days after the bite. Courtesy of Dale Losher.
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Media file 10:  Spider bite, brown recluse. Nine days after the bite. The patient endured 8 days with an open wound to drain the spider's toxins and needed intravenous antibiotics and pain medication almost 24 hours a day. Courtesy of Dale Losher.
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Media file 11:  Spider bite, brown recluse. Eleven days after the bite. A 5-inch wide area of dead tissue was excised, necessitating skin grafting. Courtesy of Dale Losher.
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Media file 12:  Spider bite, brown recluse. Waiting to see skin graft results 38 days after the bite. Courtesy of Dale Losher.
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Media file 13:  Spider bite, brown recluse. Skin graft results 38 days after the bite. Courtesy of Dale Losher.
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Media file 14:  Spider bite, brown recluse. View of healed wound approximately 10 months after bite. Courtesy of Dale Losher.
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Media file 15:  Dermonecrotic arachnidism represents a local cutaneous injury with tissue loss and necrosis.
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REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

• Barrett SM, Romine-Jenkins M, Fisher DE. Dapsone or electric shock therapy of brown recluse spider envenomation?. Ann Emerg Med. Jul 1994;24(1):21-5. [Medline].
• Burton KG. Nitroglycerine patches for brown recluse spider bites. Am Fam Physician. May 1 1995;51(6):1401. [Medline].
• Graham WR Jr. Adverse effects of dapsone. Int J Dermatol. Sep 1975;14(7):494-500. [Medline].
• Hobbs GD, Anderson AR, Greene TJ, Yealy DM. Comparison of hyperbaric oxygen and dapsone therapy for loxosceles envenomation. Acad Emerg Med. Aug 1996;3(8):758-61. [Medline].
• King LE Jr, Rees RS. Dapsone treatment of a brown recluse bite. JAMA. Aug 5 1983;250(5):648. [Medline].
• Lowry BP, Bradfield JF, Carroll RG, Brewer K, Meggs WJ. A controlled trial of topical nitroglycerin in a New Zealand white rabbit model of brown recluse spider envenomation. Ann Emerg Med. Feb 2001;37(2):161-5. [Medline].
• Mack RB. The bite of the spider woman. Loxosceles reclusa (the brown recluse). N C Med J. May 1992;53(5):200-3. [Medline].
• Maynor ML, Moon RE, Klitzman B, Fracica PJ, Canada A. Brown recluse spider envenomation: a prospective trial of hyperbaric oxygen therapy. Acad Emerg Med. Mar 1997;4(3):184-92. [Medline].
• Miller LG, Spellberg B. Spider bites and infections caused by community-associated methicillin-resistant Staphylococcus aureus. Surg Infect. Fall 2004;5(3):321-2. [Medline].
• Phillips S, Kohn M, Baker D, Vander Leest R, Gomez H, McKinney P, et al. Therapy of brown spider envenomation: a controlled trial of hyperbaric oxygen, dapsone, and cyproheptadine. Ann Emerg Med. Mar 1995;25(3):363-8. [Medline].
• Rees R, Campbell D, Rieger E, King LE. The diagnosis and treatment of brown recluse spider bites. Ann Emerg Med. Sep 1987;16(9):945-9. [Medline].
• Sams HH, Hearth SB, Long LL, Wilson DC, Sanders DH, King LE. Nineteen documented cases of Loxosceles reclusa envenomation. J Am Acad Dermatol. Apr 2001;44(4):603-8. [Medline].
• Vetter RS, Barger DK. An infestation of 2,055 brown recluse spiders (Araneae: Sicariidae) and no envenomations in a Kansas home: implications for bite diagnoses in nonendemic areas. J Med Entomol. Nov 2002;39(6):948-51. [Medline].
• Vetter RS, Bush SP. Reports of presumptive brown recluse spider bites reinforce improbable diagnosis in regions of North America where the spider is not endemic. Clin Infect Dis. Aug 15 2002;35(4):442-5. [Medline].
• Wille RC, Morrow JD. Case report: dapsone hypersensitivity syndrome associated with treatment of the bite of a brown recluse spider. Am J Med Sci. Oct 1988;296(4):270-1. [Medline].
• Wright SW, Wrenn KD, Murray L, Seger D. Clinical presentation and outcome of brown recluse spider bite. Ann Emerg Med. Jul 1997;30(1):28-32. [Medline].
• Dyachenko P, Ziv M, Rozenman D. Epidemiological and clinical manifestations of patients hospitalized with brown recluse spider bite. J Eur Acad Dermatol Venereol. Oct 2006;20(9):1121-5. [Medline].

Article Last Updated: Jun 7, 2007