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January 1961

Arachnidism by Loxosceles Laeta: Report of 40 Cases of Necrotic Arachnidism

Author Affiliations


From the Department of Dermatology, University of Chile (Florencio Prats, Professor), Dermatology Clinic of the University J. J. Aguirre Hospital, and the Department of Parasitology of the University of Chile.

Arch Dermatol. 1961;83(1):139-142. doi:10.1001/archderm.1961.01580070145016

Arachnidism produced by the bite of Loxosceles laeta, a common house spider encountered in South America, may present 2 clinical pictures: the localized cutaneous necrotic loxoscelism, and the severe systemic hemoglobinuric viscerocutaneous loxoscelism.

In this report we present an epidemiological, clinical, and therapeutic study of 40 cases personally observed by us, of which 4 cases were of the severe form. Twenty-seven of these cases were the subject of 2 former publications.5,6

The Spider  Loxosceles laeta exists in most of South America, and it has been found especially in Chile,4 Uruguay,2 and Peru.3,7 The body of the spider is 1.5 cm. in length, yellowishbrown, the abdomen being darker than the cephalothorax. The legs are long and covered with fine hairs (Fig. 1). It is found inside old houses, in cracks in the walls and ceilings, behind pictures or furniture, and inside clothing. It does not attack, but

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