B. Systemic Loxoscelism

Systemic loxoscelism is a constitutional illness resulting from the bite of a spider from the genus Loxosceles. In the US this is most commonly from the spider known colloquially as the brown recluse spider, which is endemic to the South and Midwest. The bite of the Loxosceles is usually painless initially. Pain typically develops 2-8hrs after envenomation along with redness at the site of the bite. In rare cases this will progress to a dusky lesion with depressed center which develops into a dry eschar that subsequently ulcerates – this is known as necrotic arachnoidism and was seen in the patient in this case.   The venom of the Loxosceles contains phospholipases D, formerly known as sphingomyelinase, which is thought to cause the majority of damage. It exerts its effects by activating complement and inducing neutrophil chemotaxis and apoptosis of effected cells. Because the bite of Loxosceles is usually initially painless the frequency of systemic loxoscelism after a bite is unknown, but is thought to be rare. When it does occur it manifests as massive hemolysis, hemoglobinuria, acute renal failure, disseminated intravascular coagulation, and rarely death. Treatment of systemic loxoscelism includes supportive care. It is unclear if glucocorticoids or IVIg have any benefit, but can be considered.

Ulceroglandular tularemia is the most common form of tularemia. It is characterized by skin lesions and associated adenopathy. Tularemia itself is caused by infection with Francisella tularensis, an aerobic and fastidious gram-negative bacterium. Human infection occurs following contact with infected vectors – ticks being the most common.   Pyoderma gangrenosum is a rare neutrophilic dermatosis that presents as an inflammatory and ulcerative disorder of the skin. Despite its name it is neither infectious nor gangrenous. It is most commonly found in patients with an underlying disease; inflammatory bowel disease, hematologic diseases, and rheumatic arthridities  are most frequent. It is a diagnosis of exclusion as the clinical, histopathologic, and laboratory findings are nonspecific.   Granulomatosis with polyangitis (Wegener’s granulomatosis) is an antineutrophilic cytoplasmic autoantibody (ANCA) associated vasculitis. Hematuria and cutaneous manifestations, including focal necrosis and ulceration, can be noted on presentation. “Classically” patients also present with a history of both upper and lower respiratory tract symptoms as well (E.g. epistaxis and hemoptysis). A positive ANCA test in the setting of strong clinical suspicion, suggests the diagnosis. However, diagnosis is confirmed by biopsy from a site of active disease.   Epinephrine-associated gangrene is a local manifestation of epinephrine injection most commonly seen after injection of local anesthetics in combination with epinephrine. It is an ischemic process due to the vasoconstrictive properties of epinephrine and is fortunately very rare with accidental EpiPen injections.

References

Divito SJ, Haught JM, English JC, III, Ferris LK. An Extensive Case of Dermonecrotic Arachnidism. J Clin Aesthet Dermatol 2009;2:40. Robinson JR, Kennedy VE, Doss Y, Bastarache L, Denny J, Warner JL. Defining the complex phenotype of severe systemic loxoscelism using a large electronic health record cohort. PLoSOne 2017;12.

Tambourgi D V., Paixão-Cavalcante D, Andrade RMG de, Fernandes-Pedrosa M de F, Magnoli FC, Morgan BP, et al.Loxosceles Sphingomyelinase Induces Complement-Dependent Dermonecrosis, Neutrophil Infiltration, and Endogenous Gelatinase Expression. J Invest Dermatol 2005;124:725–31

Wright SW, Wrenn KD, Murray L, Seger D. Clinical Presentation and Outcome of Brown Recluse Spider Bite. Ann Emerg Med1997;30:28–32. Nguyen N, Pandey M. Loxoscelism: Cutaneous and Hematologic Manifestations. Adv Hematol 2019;2019.