Necrotic Arachnidism

Violin spiders, Loxosceles, most often produces necrotic arachnidism. Lox-osceles laeta inhabits Latin America; L. reclusa, the brown recluse, in the United States, and L. refuscens, the Mediterranean and adjacent nations. Related species occur in Africa. The spider's outdoor preferences include the undersurfaces of rocks and boards, and caves; indoors, they prefer dark, dry locations, such as closets, storage spaces, drawers, and garages. Bites occur most often when the spider is trapped against a body part, usually while the patient dresses, on the face, neck, and hands (51,54).

The bite itself is often painless, but within a few hours the site becomes, in mild cases, mildly pruritic and painful with surrounding ischemic pallor; these changes resolve within a few days. In more severe cases, pruritis and pain last for 8 hours to a day before a blue-gray macular halo develops with or without a pustule or bulla at the inoculation site; red, swollen, purpuric skin often surrounds the halo. Necrosis, eschar, and ulceration often follow, accompanied sometimes by a swollen limb or portion of torso. These changes usually happen within the first to third days. Resolution by a scar can take half a year. Local complications include chronic pain, secondary infection, skin graft failure, pyoderma gangrenosa, and limb function impairment (54,56). Treatment may involve surgery, which is beyond the scope of this text.

Necrotic areas narrower than 2 cm may require only pain medicine, anti-histamines, sterile dressings, tetanus prophylaxis, ice, and elevation of the affected limb. Necrotic foci larger than 1 cm require screening for hemolysis, renal failure, and disseminated intravascular coagulation. Mild systemic reactions are usually apparent within 3 days and include leukocytosis, malaise, headache, arthralgia, myalgia, proteinuria, vomiting, diarrhea, and generalized urticaria. Severe reactions include anuria, delirium, shock, hemolysis, and coma. These reactions should prompt consideration of hospitalization.

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