Loxoscelismo: revisión de la literatura a propósito de un caso / Loxoscelism: Literary review about a case

La mordedura de la araña de rincón es un motivo de consulta frecuente en los servicios de urgencia de Chile, que puede producir un cua-dro severo con manifestaciones cutáneas y sistémicas. En Chile, Loxocelles laeta se ubica principalmente desde la I a la VIII región, aunque se han reportado casos de loxocelismo en todo el país. El veneno de esta araña tiene efecto cutáneo-necrosante, hemolítico, vasculítico y coagulante. Podemos identificar 3 tipos de loxocelismo: cutáneo necrótico (80% de los casos), cutáneo edematoso (5%) y cutáneo visceral (10-15%). Este último tiene una letalidad entre 1 y 3% del total de casos de loxocelismo, la cual depende en gran parte de la precocidad de su diagnóstico y manejo oportuno. Se debe controlar cualquier tipo de loxocelismo durante las primeras 24 a 48 horas y vigilar la aparición de síntomas y signos sugerentes del cuadro visceral. No existe ningún examen de laboratorio que confirme el diagnóstico, los cuales sólo se alteran de modo marcado en los casos viscerales. El manejo de las lesiones cutáneas es con hielo local, antiinflamatorios, antihistamínicos y curaciones seriadas. En caso del loxocelismo visceral, el tratamiento principal es de soporte. La dapsona fue una indicación frecuente en el pasado y se asocia a efectos adversos graves, siendo el principal la exacerbación de la hemólisis, por lo que actualmente su uso no está recomendado. El suero anti-loxoceles no tiene evidencia que avale menor severidad ni mortalidad del cuadro.

The bite of the corner spider is a frequent reason for consultation in the emergency services of Chile, which can produce a severe reaction with cutaneous and systemic manifestations. In Chile, Loxocelles laeta is located mainly in the first to the eighth region, but cases of loxoscelism are reported throughout the country. The venom of this spider has cutaneous-necrotizing, hemolytic, vasculitic, and coagulant effects. Three types of loxoscelism can be identified, necrotic cutaneous (80% of cases), edematous cutaneous (5%), and visceral cutaneous (10-15%). The latter has a lethality between 1 and 3% of all cases of loxoscelism, which largely depends on the early diagnosis and timely management. Any loxoscelism should be controlled during the first 24 to 48 hours, and be alert to the appearance of symptoms and signs suggestive of visceral manifestations. There isn ́t any laboratory test to confirm the diagnosis. Laboratory tests are only markedly altered in visceral cases. The management of skin lesions is with local ice, NSAIDs, antihistamine and serial dressings. In the case of visceral loxoscelism, treatment begins with suspicion and early diagnosis. For these patients, the principal treatment is supportive care. Although it was recommended in the past, Dapsone is associated with severe adverse effects, like exacerbation of he-molysis, so its use is not currently recommended. The anti-loxocelles serum has no evidence to support less severity or mortality reduction.

Temporal evolution of dermonecrosis in loxoscelism assessed by photodocumentation

ABSTRACT Background: Although loxoscelism (bites by brown spiders of the genus Loxosceles) frequently results in dermonecrosis, no previous clinical reports have provided detailed temporal photodocumentation of the evolution of dermonecrotic lesions in a case series. Methods This was a retrospective cohort study involving a case series of loxoscelism. Only cases of dermonecrosis with photodocumentation of lesion evolution (from admission until complete or almost complete healing) were included. Results: Eight patients (six men, two women; median age, 38 years) fulfilled the inclusion criteria. The bite sites included the thigh (n = 4), forearm (n = 2), abdomen (n = 1), and trunk (n = 1). Time interval between the bite and first contact with our service ranged from 15 to 216 h (median = 29 h). The main clinical manifestations included local erythematous and ischemic violaceous lesions overlying a base of indurated edema (livedoid plaque, 8), local pain (8), exanthema (6), serohemorrhagic vesicles/blisters (5), fever (5), and jaundice (1). Based on a previously established classification, the cases were classified as probable cutaneous-necrotic loxoscelism (CNL, n = 4), presumptive CNL (n = 3), and presumptive cutaneous-hemolytic loxoscelism (n = 1). Seven patients were treated with anti-arachnidic antivenom (AV; median time post-bite = 46 h). Complete lesion healing ranged from 34 to 98 days post-bite (median, 68 days; six patients). None of the patients required reconstructive plastic surgery. Conclusions The sequential photographic documentation showed considerable variation in the process of wound healing, with complete epithelialization requiring up to 3 months after the bite.

Highlights in the knowledge of brown spider toxins

Abstract Brown spiders are venomous arthropods that use their venom for predation and defense. In humans, bites of these animals provoke injuries including dermonecrosis with gravitational spread of lesions, hematological abnormalities and impaired renal function. The signs and symptoms observed following a brown spider bite are called loxoscelism. Brown spider venom is a complex mixture of toxins enriched in low molecular mass proteins (4-40 kDa). Characterization of the venom confirmed the presence of three highly expressed protein classes: phospholipases D, metalloproteases (astacins) and insecticidal peptides (knottins). Recently, toxins with low levels of expression have also been found in Loxosceles venom, such as serine proteases, protease inhibitors (serpins), hyaluronidases, allergen-like toxins and histamine-releasing factors. The toxin belonging to the phospholipase-D family (also known as the dermonecrotic toxin) is the most studied class of brown spider toxins. This class of toxins single-handedly can induce inflammatory response, dermonecrosis, hemolysis, thrombocytopenia and renal failure. The functional role of the hyaluronidase toxin as a spreading factor in loxoscelism has also been demonstrated. However, the biological characterization of other toxins remains unclear and the mechanism by which Loxosceles toxins exert their noxious effects is yet to be fully elucidated. The aim of this review is to provide an insight into brown spider venom toxins and toxicology, including a description of historical data already available in the literature. In this review article, the identification processes of novel Loxosceles toxins by molecular biology and proteomic approaches, their biological characterization and structural description based on x-ray crystallography and putative biotechnological uses are described along with the future perspectives in this field.(AU)

Highlights in the knowledge of brown spider toxins

Abstract Brown spiders are venomous arthropods that use their venom for predation and defense. In humans, bites of these animals provoke injuries including dermonecrosis with gravitational spread of lesions, hematological abnormalities and impaired renal function. The signs and symptoms observed following a brown spider bite are called loxoscelism. Brown spider venom is a complex mixture of toxins enriched in low molecular mass proteins (440 kDa). Characterization of the venom confirmed the presence of three highly expressed protein classes: phospholipases D, metalloproteases (astacins) and insecticidal peptides (knottins). Recently, toxins with low levels of expression have also been found in Loxosceles venom, such as serine proteases, protease inhibitors (serpins), hyaluronidases, allergen-like toxins and histamine-releasing factors. The toxin belonging to the phospholipase-D family (also known as the dermonecrotic toxin) is the most studied class of brown spider toxins. This class of toxins single-handedly can induce inflammatory response, dermonecrosis, hemolysis, thrombocytopenia and renal failure. The functional role of the hyaluronidase toxin as a spreading factor in loxoscelism has also been demonstrated. However, the biological characterization of other toxins remains unclear and the mechanism by which Loxosceles toxins exert their noxious effects is yet to be fully elucidated. The aim of this review is to provide an insight into brown spider venom toxins and toxicology, including a description of historical data already available in the literature. In this review article, the identification processes of novel Loxosceles toxins by molecular biology and proteomic approaches, their biological characterization and structural description based on x-ray crystallography and putative biotechnological uses are described along with the future perspectives in this field.

Acidente loxoscélico / Loxoscelic accident

Os acidentes com aranhas do gênero Loxosceles podem apresentar variadas evoluções clínicas, dificultando a realização do diagnóstico e a escolha correta de uma medida terapêutica. Este artigo de revisão tem como objetivo abordar os mais importantes mecanismos de evolução, principais desfechos e os tratamentos de escolha para o acidente loxoscélico (AU)

Accidents with Loxosceles genus spiders may have different clinical outcomes, hindering the diagnosis and the correct choice of a therapeutic measure. This review article aims to address the main mechanisms of evolution, main outcomes and treatments of choice for loxoscelic accident (AU)

Development of Loxosceles intermedia Mello-Leitão (1934) (Araneae, Sicariidae) genital tract / Desenvolvimento do trato genital de Loxosceles intermedia Mello-Leitão (1934) (Aranea: Sicariidae)

We examined the post-embryonic development of the male and female genital apparatus of the brown spider, Loxosceles intermedia. The development of the genital apparatus for both sexes begins with the appearance of inner structures. In the male genital apparatus, formation of the testes occurs first, followed by differentiation of the duct, ampulla and vas deferens, and finally the formation of the genital opening and differentiation of the copulatory organ (secondary sexual characteristic). Similarly, the development of the female genital apparatus begins with the formation of the ovaries, followed by the appearance of oocytes in vitellogenesis, then the development of oviducts and uterus internus and, finally, the spermatheca. These data may be very important in further comparative studies on the development of the reproductive system of spiders.

Examinamos o desenvolvimento pós-embrionário do aparelho genital masculino e feminino da aranha-marrom Loxosceles intermedia. O desenvolvimento do aparelho genital de ambos os sexos começa com o aparecimento de estruturas internas. No aparelho genital masculino a formação dos testículos ocorre primeiro, seguida pela diferenciação do ducto, ampola e vas deferens e, finalmente, a formação da abertura genital e diferenciação do órgão copulador (característica sexual secundária). Da mesma forma, o desenvolvimento do aparelho genital feminino começa com a formação dos ovários, seguida pelo aparecimento de oócitos em vitelogênese, o desenvolvimento dos ovidutos e uterus internus e, finalmente, a espermateca. Esses dados podem ser muito importantes em estudos comparativos sobre o desenvolvimento do sistema reprodutivo de aranhas.