Loxoscelism symbolizes dermonecrotic lesions and systemic manifestations incurred by the brown recluse spider bite (Barretto, Soeiro Prestes, Figueiredo Fonseca, & Achucarro Silveira, 2007). Generally, brown recluse spider bites are asymptomatic. The brown recluse (Loxosceles) is one of 100,000 species of spiders worldwide and considered to be one of the most medically significant assemblies of spiders (Dyachenko, 2005). Its bite can cause severe skin necrosis. Another spider type worth mentioning is black widow (Latrodectus). The black spider is tiny, shady black, with a red hourglass mark on its belly, and found frequently in low-lying webs in garages, around swimming pools, and in wood piles. Their bite occurs between April and October defensively, and it is more venomous. The brown spider is long with a violin mark on the upper back, and lives in hot, dry abandoned areas such as woods, rocks, and bed linen (Nehemya, 2008). However, black widow bites are more notorious than the recluse; for every black widow bite, there are hundreds of brown recluse bites documented (Nehemya, 2008).
Typically, the area affected becomes intensely painful, with localized erythema and edema within 2–3 hours of the bite. A central bulla develops in 12–24 hours, followed by an area of central necrosis. Presentations can vary and systemic symptoms are unusual (Dyachenko, 2005; Nunnelee, 2006). The patient was not aware of being bitten; however, the diagnosis was made on the basis of the history and the typical appearance of the lesion (Nehemya, 2008). She presented with a mild form of spider bite. The lesion did not exhibit bulla formation, which may have been masked by the scratching due to the severe itching. The ulcerative lesion over her posterior thigh developed within the first 2 days, and is likely the site of the spider bite (see Figure 1).
Researchers speculate spider venom is responsible for the patho-physiological features of the bite (necrotic ulcer). When the spider bites, it injects cytotoxic venom, which carries many potent enzymes: alkaline phosphatase, 5-ribonucleotide phosphohydrolase, lipase, protease, esterase, hyaluronidase. The most important and active enzyme is sphingomyelinase-D (Forrester, Barrett, & Campbell, 1978). It was believed that sphingomyelinase enzyme is the sole cause for haemolysis, plus cutaneous and systemic reactions as was explored by Forrester and colleagues (1978). Later, this venom was projected to cause the dermo-necrosis by Patel, Modur, and Zimmerman (1994). This was explained by initiating a reaction in the vascular endothelium by activating complements, which will attract the polymorphic neutrophils, and the latter will attach to endothelium and induce reaction by releasing its granules (proteolytic enzymes, cytokine, and chemokine) (Hogan, Barbaro, & Winkel, 2004). This mechanism starts by inducing the release of E-selectin which causes release of cytokines; namely interleukin-8 and granulocyte macrophage colony-stimulating factor. Both cytokines act as key mediators in the attraction and activation of neutrophils, whereby the neutrophils bind to E-selectin, then degranulate and cause tissue destruction. Thus platelet aggregation and blood flow alterations occur (Hogan et al., 2004), resulting in edema and ischemia and necrosis locally.
Dermatology Nursing. 2010;22(3):39-42. © 2010 Jannetti Publications, Inc.
Cite this: An Elderly Diabetic Patient with Necrotic Arachnidism - Medscape - May 01, 2010.