The diagnosis of spider bite is a speculative diagnosis (Diaz & Kim, 2007; Rhoads, 2006), but other causes should be considered and excluded, mostly MRSA. Other major differential diagnoses can be considered in this condition and should be ruled out, such as ecthyma, leishmaniasis, diabetic ulcer, pyoderma gangrenosum, and deep fungal infection. In this case, the history of a sudden sting on the posterior thigh followed by ulcer development made the clinical diagnosis of the necrotic arachnidism explicit.
Usually spiders bite humans when the victim accidentally comes into physical contact when the spider is trapped or crushed against the skin while sleeping, dressing, etc. (Bitterman-Deutsch, Bergman, & Friedman-Birnbaum, 1990; Diaz & Kim, 2007). The most common areas affected are limbs and face (Schenone, 2003). The nature and severity of the lesion varies by case. Predictors of a rapid healing involve mild edema and erythema and minimum necrosis at presentation. Management decisions stipulate cautious consideration of exact location of the bite, degree of envenomation, age, and general circumstances of the patient health (Bitterman-Deutsch et al., 1990; Furbee, Kao, & Ibrahim, 2006). Elevated ESR in this case can be explained on the basis of her chronic illness (diabetes for 10 years on insulin injection).
Clinical manifestations seen at the loxoscelicm envenomation site can range from a mild, self-limiting, local, skin necrosis; either in form of a mild cutaneous reaction (mild erythema) or a severe skin necrosis (necrotic arachnidism), to a less commonly, potentially severe muscle necrosis (rhabdomyolysis), hemolysis (blood lysis), coagulopathy (blood coagulation disorders), disseminated intravascular coagulation resulting in acute renal failure, and electrolyte disorders (da Silva et al., 2004; de Souza et al., 2008; Forks, 2000; França, Barbaro, & Abdulkader, 2002; Futrell, 1992; Majeski & Durst, 1976; Peterson, 2006; Ribeiro et al., 2007; Robb, Hayes, & Boyd, 2007; Senff-Ribeiro et al., 2008; van den Berg, Gonçalves-de-Andrade, Magnoli, & Tambourgi, 2007; Wright, Wrenn, Murray, & Seger, 1997). Furthermore, the skin lesion could heal slowly, persisting for a few months, leaving a deep scar (Forks, 2000; Peterson, 2006; Wright et al., 1997).
As Figure 1 displays, there is a small necrotic area (2 x 3 cm) on the right posterior thigh, as most spider bites occur at the lower extremities. The patient's major concern initially was her extreme discomfort. The patient recovered gradually over the following weeks. She showed a dramatic improvement of the redness and swelling during her weekly followup visits (see Figures 1–3). By week 4 the lesion had resolved dramatically (see Figure 3), and the patient felt well and completely satisfied. She did not return for followup after week 4.
The major drawback, losing patients to followup, sometimes makes predication of the outcome difficult. Nonetheless, ongoing research suggests the long-term sequelae after brown recluse bite is good. In this case, the bite healed with supportive care alone, and therefore aggressive treatment does not appear warranted, as in fact serious complications are rare in the majority of the spider bites cases (Wright et al., 1997).
Dermatology Nursing. 2010;22(3):39-42. © 2010 Jannetti Publications, Inc.
Cite this: An Elderly Diabetic Patient with Necrotic Arachnidism - Medscape - May 01, 2010.