Brown recluse spider bite

Pathogenesis Synonym(s)

Proposed mechanisms including photode- Necrotic arachnidism; arachnidism; struction of porphyrin and deposition in loxoscelism; latrodectism

106 Brown spot syndrome

Brown recluse spider bite. Plaque with early necrosis in the center and an erythematous border,,


Skin necrosis and sloughing secondary to the bite of the brown recluse spider


Envenomation from brown recluse spider (Loxosceles reclusa); phospholipase D main toxic factor

Clinical manifestation

Bite minimally symptomatic; fewer than 10% of bites result in severe skin necrosis; signs of progression within 48-72 hours of the bite; mild-to-severe pain beginning 2-8 hours after bite; central papule and associated erythema occur 6-12 hours after bite; purple vesicle sometimes ulcerates; stellate necrotic area sometimes ensues. Constitutional signs and symptoms: hemol-ysis; hemoglobinuria; thrombocytopenia; disseminated intravascular coagulation; fever; headache; malaise; arthralgia; nausea; vomiting

Differential diagnosis

Pyoderma gangrenosum; ecthyma; herpes simplex virus infection; insect bite reaction; squamous cell carcinoma; coumarin necrosis; vasculitis; vascular insufficiency; necrotizing fasciitis; factitial ulceration; thromboembolic phenomenon; skin trauma; thromboangiitis obliterans; neuropathic ulceration; tularemia; mucormycosis


Local therapy: cleansing of the bite site; cold compresses; simple analgesics; elevation of an affected extremity; intralesional corticosteroids

Systemic therapy: dapsone; prednisone for systemic signs and symptoms Surgical therapy: excision of necrotic area only after 6 weeks if healing not progressing


Sams HH, Dunnick CA, Smith ML, King LE Jr (2001) Necrotic arachnidism. Journal of the American Academy of Dermatology 44(4)^61-573

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