September 2003
Diagnosis: Life-threatening head and neck edema secondary to probable brown recluse spider bite of the lip
On admission to Children's Hospital, the etiology of the patient's facial swelling was unclear. The patient was suspected to have angioedema and underwent an extensive evaluation. All laboratory results were within normal limits. Imaging of the head and neck revealed extensive soft tissue swelling. As the edema improved and the area of necrosis became visible, a brown recluse bite was suspected. Upon further interview, the patient's father reported seeing a brown spider in the area of the hide-a-bed. Based on the patient's history, the presence of a brown spider, and a clinically compatible lesion, a diagnosis of probable brown recluse bite was made.
Discussion:
The brown recluse (Loxosceles reclusa) is a small brown venomous spider characterized by six eyes and a distinctive violin-shaped mark on its dorsal cephalothorax. L. reclusa is a nocturnal spider that prefers secluded areas and preys at night on insects and other spiders. This shy spider avoids humans but bites when threatened or injured.
Loxosceles toxin is designed to paralyze and digest small prey. The effect it has on human tissue is incidental. The venom contains multiple enzymes and proteins including alkaline phosphatase, esterase, hyaluronidase, and sphingomyelinase D2. Frequently stomach enzymes such as lipase and protease contaminate bites and potentiate tissue injury. Sphingomyelinase D2 is the major component of brown recluse venom. It has multiple effects including direct erythrocyte lysis, complement activation, platelet aggregation, and myelin sheath degradation. Hyaluronidase contributes to tissue fluidity and resultant gravitational spread. Lipase is responsible for the characteristic depressed scarring. It is believed that the resultant tissue necrosis is, in large part, due to neutrophil activation.
Brown recluse spider bites are a relatively common problem in the U.S. and occur most frequently in the midwest and southcentral states. Envenomation can result in a broad spectrum of clinical presentations. Most patients with brown recluse bites have an excellent outcome. Only 10-15% of brown recluse bites result in major morbidity with scarring, hospitalization, or prolonged wound healing. Cutaneous reactions to envenomation range from minimal erythema to severe full thickness skin necrosis. Several factors contribute to the severity of the cutaneous wound including the anatomic site involved, the amount of venom injected, inclusion of gastric contents, and host susceptibility. Pain is characteristic and may be severe. Edema can be pronounced. In 1996, Goto et al reported a similar case of upper airway obstruction secondary to a documented brown recluse spider bite on the neck. A small minority of envenomations result in a systemic reaction consisting of fever, chills, malaise, nausea, vomiting, and a morbilliform rash. Rarely, severe systemic toxicity results in hemolytic anemia, thrombocytopenia, disseminated intravascular coagulation, renal failure, and even death.
Brown recluse spider bites are often difficult to diagnose definitively. Only one in ten patients bring in the spider for identification, which is the gold standard for diagnosis. No laboratory test exists to readily identify a victim of envenomation. Therefore, bites are classified as putative, presumptive, probable, and documented based on the patient's history and physical examination.
Treatment of a brown recluse bite should be based on the severity of the patient's lesion and whether systemic toxicity is exhibited. Conservative treatment with thorough cleansing followed by rest, ice, compression, and elevation (RICE) is indicated for mild localized lesions without systemic involvement. The vast majority of envenomation victims fare well with minimal thrapy. For more severe cutaneous lesions with necrosis or ulceration, antibiotics should be initiated to prevent secondary infection. Aspirin can be used to counteract platelet aggregation. Pain and pruritus should be treated with analgesics and antihistamines respectively. Heat should be avoided as it potentiates the venom's enzymatic activity. The use of Dapsone for necrotic arachnidism is controversial. Dapsone works by inhibiting neutrophil migration and function. Theoretically through this mechanism of action, Dapsone may assist in limiting neutrophil induced cutaneous necrosis. No controlled human trials utilizing Dapsone for brown recluse envenomation exist and animal studies to date are equivocal. One must, therefore, carefully weigh the risk-benefit ratio prior to implementing Dapsone therapy. Early surgical intervention should be avoided. Premature or aggressive surgical intervention has been shown to increase inflammation and potentiate venom effects. Instead, gentle debridement should be performed only after the wound has stabilized and the inflammation has subsided. For patients with systemic symptoms, serial CBC's and urinalyses are advocated to monitor for hemolytic anemia, thrombocytopenia, and renal complications. Patients should be aggressively hydrated to maximize renal perfusion. Systemic steroids (Prednisone 1-2 mg/kg/day) have been reported to lessen hemolysis and protect kidney function, especially in young victims. Numerous other anecdotal therapies have been advocated including hyperbaric oxygen, antivenom, heparin, and nitroglycerin.
References:
1. Goto C, Abramo T, Ginsburg C. Upper Airway Obstruction Caused
by Brown Recluse Spider Envenomization of the Neck. Am J Emerg
Med 1996;14:660-2.
2. Sams H, Dunnick C, Smith M, King L. Necrotic Arachnidism. J
Am Acad Dermatol 2001;44:561-73.
3. Sams H, King L. Brown Recluse Spider Bites. Dermatol Nurs 1999;11:427-433.
4. Wright S, Wrenn K, Murray L, Seger D. Clinical Presentation
and Outcome of Brown Recluse Spider Bite. Ann Emerg Med 1997;30:28-32.
My thanks to Dr. Angela Sprague for providing this case for presentation. Thanks for your help.