Escharotic Lesion After a “Brown Recluse Spider Bite”
Am Fam Physician. 2007 Jun 15;75(12):1841-1842.
A 63-year-old woman presented with what she thought was a brown recluse spider bite received 10 days earlier. After noticing a small, painless, nonpruritic, red bump on her upper back, she surmised that a spider had bitten her, although she did not see a spider at the time. The following day she applied a “black salve” she had learned about in a local traditional medicines class. A black eschar soon developed, and the lesion became progressively pruritic.
Her medical history was remarkable for a basal cell carcinoma, excised from a separate location on her back seven years ago, and for well-controlled psoriasis. The physical examination revealed a 1-cm concentric black eschar surrounded by a 2-mm fissure and a 4-mm ring of erythema (see accompanying figure) on her upper back.
Based on the patient's history and physical examination, which one of the following is the most likely diagnosis?
A. Brown recluse bite.
B. Cutaneous anthrax.
D. Reaction to black salve.
E. Recurrent basal cell carcinoma.
The answer is D: a reaction to black salve. Black salve is an escharotic compound typically containing bloodroot (Sanguinaria canadensis). Traditionally, it is used by Native Americans as an orange dye and herbal medicine. It was first described in the 1800s as a topical salve used to treat breast cancer and other solid tumors.1 Although recent laboratory studies suggest potential future applications, no clinical data currently support its use for cancer treatment.2 However, it has been used in the past as part of the Mohs surgical technique as a chemical fixative before the procedure.2,3
Bloodroot contains sanguinaria, a toxic alkaloid with antimicrobial, antifungal, and anti-inflammatory properties.1,4,5 Toxic alkaloids are corrosive, causing tissue necrosis and formation of a black eschar.6 Exaggerated curative properties of bloodroot are advertised on products and Web sites.
Approximately 80 percent of reported “spider bites” are caused by nonarachnid sources.7 The tissue necrosis visible in the accompanying figure could be consistent with a brown recluse spider bite; however, the clinical history and onset of symptoms are not. The typical brown recluse bite is painful and associated with development of a lesion within 10 minutes. Infarction at the site presents as a sinking blue macule; surrounding erythema develops two to eight hours later. Forty percent of these bites result in central necrosis, and 20 percent develop severe necrosis.8
Cutaneous anthrax develops as a result of Bacillus anthracis spores entering the body through mucous membranes or breaks in the skin. Average rates in the United States were less than one case per year before the 2001 outbreak. Cutaneous anthrax typically occurs on the arms, face, and neck. A pruritic papule develops within one week of infection and progresses to a 1- to 2-cm vesicle surrounded by nonpitting edema. Rupture and necrosis then occur, followed by a black eschar.
Ecthyma, a type of impetigo, typically begins with discrete vesicles. It is followed by erosion, ulceration, and finally an asymmetrically shaped eschar. This process results from dermal extension of the infection, causing a vasculitis.
Basal cell carcinoma is a malignant tumor of the skin originating from basal cells of the epidermis. It typically begins as a smooth, pink to red nodule with pearly borders. Ulceration and crusting occur with enlargement. This occurs over a longer period than described in this case.
Selected Differential Diagnosis of a Black Eschar
Selected Differential Diagnosis of a Black Eschar
Brown recluse spider bite
Painful bite and lesion within 10 minutes; sinking blue macule with surrounding erythema develops later; central necrosis in 40 percent of bites
Pruritic papule develops within one week of infection; evolves into 1- to 2-cm vesicle surrounded by nonpitting edema; rupture and necrosis occur; black eschar follows
Begins with discrete vesicles, followed by erosion, ulceration, and finally an irregularly shaped eschar
Reaction to “black salve”
Immediate symmetric necrosis after application of salve
Basal cell carcinoma
Smooth, pink to red nodule with pearly borders; ulceration and crusting occur with enlargement
1. Harkrader RJ, Reinhart PC, Rogers JA, Jones RR, Wylie RE 2nd, Lowe BK, et al. The history, chemistry and pharmacokinetics ofSanguinaria extract. J Can Dent Assoc. 1990;56(7 suppl)7–12.
2. Jellinek N, Maloney ME. Escharotic and other botanical agents for the treatment of skin cancer: a review. J Am Acad Dermatol. 2005;53:487–95.
3. Mohs FE. Chemosurgery for facial neoplasms. Arch Otolaryngol. 1972;95:62–7.
4. Becci PJ, Schwartz H, Barnes HH, Southard GL. Short-term toxicity studies of sanguinarine and of two alkaloid extracts ofSanguinaria canadensis L. J Toxicol Environ Health. 1987;20:199–208.
5. Godowski KC. Antimicrobial action of sanguinarine. J Clin Dent. 1989;1:96–101.
6. Brinker FJ. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, Ore.: Eclectic Medical Publications, 1998.
7. Swanson DL, Vetter RS. Bites of brown recluse spiders and suspected necrotic arachnidism. N Engl J Med. 2005;352:700–7.
8. Anderson PC. Spider bites in the United States. Dermatol Clin. 1997;15:307–11.
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