Brown spider envenomation

The venom from spiders of the genus Loxosceles, the most famous being Loxosceles recluse (the most brown recluse spider) can cause serious poisoning. These spiders inhabit the south and south central states from Georgia through Texas and north to southern Wisconsin. They are commonly called violin spiders because of the violin-shaped marking on the dorsum of the cephalothorax. Many dermonecrotic lesions are incorrectly diagnosed as Brown recluse bites, as up to 50% of the diagnoses are in geographic regions of the country which do not have Loxosceles spiders. Sphingomyelinase D is the primary venom dermonecrotic factor. The toxin depletes serum hemolytic complement, prolongs the activated partial thromboplastin time and depletes clotting factors VIII, IX, XI, and XII. The venom induces rapid coagulation and occlusion of small capillaries, causing subsequent tissue necrosis. A classic "bulls eye" lesion develops, an erythematous area inside of which is a pale ischemic region that develops a dark necrotic center as the lesion matures. Healing is slow, and these ulcers may persist for months leaving a deep scar. Systemic signs occur less commonly but can be life threatening. The most prevalent sign is a hemolytic anemia with significant hemoglobinuria. There is no specific antidote. Dapsone a leukocyte inhibitor has been shown to be effective in treating dermal lesions in animal models. Conservative therapy includes several cleanings daily with Burrow's solution and hydrogen peroxide. Systemic signs of Loxosceles envenomation are potentially fatal and should be aggressively addressed. Hospitalization and intravenous fluid therapy may be needed to maintain adequate hydration and to protect renal function.