Detection of Loxosceles venom in lesional hair shafts and skin: application of a specific immunoassay to identify dermonecrotic arachnidism.

Loxosceles spiders, of which the brown recluse is the best known, are indigenous to southcentral and southwestern regions of the United States. Loxosceles spider envenomation frequently results in painful, centrally necrotic, erythematous skin lesions that evolve over 24 to 48 hours and may take several weeks to completely heal. The diagnosis of loxoscelism is typically is based on the presence of the characteristic dermal lesion, because no definitive clinical diagnostic assay exists, and the spider is generally not available for identification. We used a rapid Loxosceles-specific enzyme immunoassay to detect spider venom in a dermal biopsy and hairs plucked from a suspicious skin lesion on the lower extremity of a 52-year-old man. This report indicates that in using a novel Loxosceles-specific immunoassay, venom can be detected in dermonecrotic skin and hair specimens for up to 4 days after envenomation.