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. These bites are not uncommon, and the complications that result are not insignificant.
Of the 13 species of Loxosceles spiders 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.
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 various species of Loxosceles are found throughout the world, the 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 so-called “epidemic” of spider bites is probably community-acquired methicillin- resistant Staphylococcus aureus (MRSA) skin infections.
The brown recluse, living up to its name, is naturally nonaggressive toward humans and prefers to live in undisturbed attics, woodpiles, and storage sheds. Brown recluses 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 recluses to also be known as fiddleback spiders. Envenomation from the brown recluse 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.
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. Necrosis is more significant in the fatty areas of the buttocks, thighs, and abdominal wall.
Additional treatment includes wound care and debridement as well as treatment with antibiotics of any bacterial infections complicating the bite. Wound cultures should be regularly obtained. Skin grafting may be necessary after 4-6 weeks of standard therapy. Aggressive treatment is necessary in order to avoid loss of digits or therapeutic limb amputations.
The most common problem is the tendency for a physician to minimize the bite. Most spider bites are innocuous and clear on their own. Unless the Brown Recluse bite is suspected and treated quickly and aggressively, serious injury may result. This could lead to litigation. If the patient is treated with Dapsone, close supervision is necessary as there are many side effects associated with the drug. Lastly, when systemic complications occur, they must be recognized and treated immediately. Delays in diagnosis and treatment have been associated with serious injury and sometimes death.
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