[Cutaneous necrotic loxoscelism. A case report].

Brown recluse (Loxosceles spp.) spiders are arachnid species known to cause necrotic arachnidism. The envenomation, described as loxoscelism, is associated with localized pain, erythema, and edema followed by the development of necrosis. However, the specific pathophysiological mechanisms by which Loxosceles venom exerts these noxious symptoms are multifactorial and not fully understood. The causative factor for production of necrotic lesions is generally considered to be the enzyme sphingomyelinase D (SMD), which cleaves sphingomyelin to form choline and ceramide 1-phosphate. Four active forms of SMD with molecular weight of 32 000 are found in L recluse. Sphingomyelinases of comparable size are also described in the venoms of Loxosceles intermedia, gaucho and laeta. Here we describe the case of a young male adult who suffered a spider bite on his left forearm which evolved into a necrotic lesion, and after a few days the injury healed completely. One week later the patient developed two similar lesions on his left leg. The diagnosis was established by clinical data and by biopsy findings. The patient did not developed systemic complications.