Brown Recluse Spider Bite: A Rare Cause of Necrotic Wounds

Pamela S. Norden, MD, MBA, and Tania J. Phillips, MD, FRCPC

A 55-year-old white woman presents with a 9-month history of nonhealing ulceration inferior to the right axilla. The patient does not recall any trauma or antecedent event but remembers cleaning a garage in northern California 3 days prior to ulcer appearance. The wound was initially small but subsequently enlarged and developed satellite ulcers. Multiple courses of both topical and oral antibiotics and topical steroids did not improve the condition. The patient reports that nonadherent granulation occurs and that the ulcer often produces clear drainage, bleeds easily, and is extremely painful. She denies that the affected site was ever blue, gray, or black in color. After months of evaluation by numerous physicians, the patient is diagnosed with a brown recluse spider bite.
Physical examination is notable for a 5 cm x 4 cm well-demarcated circular ulcer of the right lateral chest, inferior to the axilla (Figure 1). The left lateral border shows overgranulation. The right lateral aspect reveals increased depth with fibrinous exudate. Three adjacent superficial ulcers, each approximately 1 cm in diameter, are also present. The surrounding skin is notable for macular erythema. There is no cervical or axillary lymphadenopathy. The remainder of the patient’s full skin examination is within normal limits. Scars are noted on bilateral breasts from prior mastectomy and reconstruction surgery.
Has the patient been correctly diagnosed?


The brown recluse spider (Loxosceles reclusa) is the most common of the Loxosceles species in the United States.1 Human Loxosceles bites were first described in the literature1 in 1879 and were first associated with necrosis2 in 1958. While the majority of wounds caused by this spider do not require medical attention, bites may result in necrotic skin lesions, hemolysis, and renal failure. Each year, approximately 10,000 spider bites are reported to poison control centers in the US. In 1994, 1,835 of these were attributed to L. reclusa.3
The brown recluse spider is found in the southern central states of the midwestern region of the US (Figure 2).4 The heavy concentration of these spiders in this region is primarily attributable to its warm climate and moderate winters.5 Similar species found in southern California, Arizona, and Texas are known by common names, such as the desert recluse and the Arizona recluse. Many physicians incorrectly refer to all of these species as brown recluse spiders.4
Verified reports of spider travel outside of the native area are rare and almost always involve single spiders.4 Bites are uncommon in locations where spider populations are abundant and are distinctly rare in nonendemic regions. A collaborator in a 2001 study in Kansas collected more than 2,000 brown recluse spiders in her home, but no one in the home ever showed evidence of a bite.6
In contrast to the majority of spider species, which have 8 eyes, recluse spiders possess 3 pairs of eyes (dyads) on the anterior portion of the cephalothorax. The dorsum of the recluse cephalothorax is notable for a dark-brown violin-shaped marking (Figure 3). Though spiders may darken as they age and obscure the marking, these 2 findings often assist the layperson in identifying the recluse.7 Other distinguishing characteristics include an abdomen that lacks a coloration pattern and legs covered with fine hairs, in contrast to the thickened spines of other species.4 Brown recluse spiders often seek shelter in places away from plain view, such as abandoned buildings, basements, dresser drawers, stairwells, and clothing. The spider bites only when forced into contact with human skin.5

Clinical Presentation

Numerous attempts have been made to classify the clinical spectrum of loxoscelism, the condition of human envenomation by a Loxosceles spider.



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