Brown Recluse Spider Bites

As the name implies, the brown recluse spider is a reclusive organism. Humans encounter this spider in attics, storage sheds, crawl spaces, and woodpiles. Encounters with humans are uncommon.

PATHOPHYSIOLOGY Brown recluse spiders are not aggressive and bite humans in self-defense. The venom results in epidermal and subcutaneous necrosis. This reaction is a local process around the bite site.

CLINICAL FEATURES Because the bite itself is painless, patients cannot recall being bitten. Only a history of potential exposure can be elucidated. Rarely does a patient see the bite or capture the spider. About 6 to 8 h after the bite, pain associated with a red-to-violaceous discoloration develops. Two central puncture wounds are often visible on close inspection. Initially, the bite site may look like a bruise. It may even form a bulla. Over the next several hours to days, necrosis of the skin and subcutis will occur (Fig.; 242-5). This reaction may remain localized or spread to 25 cm in diameter. The spread is in a gravitational direction. Healing is very slow and results in scarring. Secondary infection is common.

Systemic symptoms are unlikely, but if they occur, the victim experiences fever, malaise, nausea, vomiting, hemolytic anemia, thrombocytopenia, disseminated intravascular coagulation, seizures, and coma.

DIAGNOSIS Diagnosis is based on history of potential exposure and clinical course. The spider varies from tan to dark brown and has a violin-shaped marking on its back. It ranges from 0.2 to 2.5 cm in length. Because of the distinct marking, the brown recluse spider is often known as the violin or fiddle-back spider.

The differential diagnosis includes necrotizing fasciitis, pyoderma gangrenosum, toxic reactions to other biting organisms, and infectious processes.

TREATMENT Initial treatment includes elevation of the affected area, inactivity, and ice compresses to decrease erythema and edema and prevent the spread of venom. Additional treatment for brown recluse spider bites is controversial and includes dapsone, d├ębridement and skin grafting, and systemic corticosteroids. For small areas of involvement, observation and prevention of secondary infection are recommended. Dapsone, a leukocyte inhibitor, has been reported to prevent progression. Dapsone doses should begin at 25 mg twice daily. Patients should be monitored closely for side effects, including hemolysis and agranulocytosis. Dapsone should not be prescribed to individuals with glucose-6-phosphate dehydrogenase deficiency.

D├ębridement and skin grafting should be delayed until wounds have stabilized, since the venom may delay wound healing. The role of systemic corticosteriods is also controversial. They are recommended for systemic symptoms. Consultation by a dermatologist or other physician with experience in bite reactions should be sought to rule out other potential causes and determine the most appropriate course of therapy. Outpatient management with close follow-up is appropriate for mild-to-moderate cases. Extensive necrosis, rapid progression, or systemic symptoms may require close monitoring in a hospital setting.

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