Cutaneous loxoscelism caused by Loxosceles similis venom and neutralization capacity of its specific antivenom.

Members of the spider genus Loxosceles pose a marked health risk to humans because of the seriousness of the necrotic and systemic effects of their bite, known as loxoscelism. The recent confirmation of Loxosceles similis in residences of Belo Horizonte in Minas Gerais Province, Brazil increases the local potential risk of loxoscelism at higher levels. The first characterization of the venom from this species showed that its main biological effects had a similar intensity as other species (e.g. Loxosceles intermedia, Loxosceles laeta, and Loxosceles gaucho). Therefore, we wished to further analyse the biological activity of the L. similis venom as well as the capacity of anti-L. similis-venom serum to reduce dermonecrotic effects to rabbit skin. Histological analysis of rabbit skin 2, 4 and 8h after intradermal injection of L. similis venom demonstrated a dense inflammatory infiltrate, edema, degeneration and necrosis of the skin muscle, dissociation of collagen fibers, and disruption of reticular fibers. Importantly, pre-incubation of the venom with anti-L. similis-venom serum significantly decreased all of these effects. Anti-L. similis antivenom generated antibodies that were strongly reactive to L. similis venom and capable of neutralizing the dermonecrotic effects in rabbits caused by this venom. Moreover, the antivenom significantly reduced the sphingomyelinase activity of L. similis crude venom. Venoms produced by male and female spiders were equally reactive towards anti-L. similis and anti-L. intermedia antivenoms, but female venom induced larger lesions on rabbits. In contrast, female venom acted as an immunization enhancer and protected animals from L. similis envenomation to a greater degree than male venom. In conclusion, the results shown in this study for L. similis antivenom merits a more in depth study of its properties, which may become a valuable tool against loxoscelism.

Odontogenic tumours in children and adolescents: a collaborative study of 431 cases.

This study describes the oral and maxillofacial pathological characteristics of a series of odontogenic tumours in children and adolescents from three Brazilian reference centres. The records were reviewed for all odontogenic tumours in patients up to 18 years old based on criteria proposed by the World Health Organization (WHO) in 2005. Data concerning sex, age, skin colour and tumour location were collected and plotted. Four hundred and thirty one odontogenic tumours in children and adolescents were found, accounting for 37.5% of the total number of odontogenic tumours diagnosed. Benign tumours were predominant (99.8% of the cases), and odontoma was the most frequent type (41.4%), followed by keratocystic odontogenic tumours (25.5%) and ameloblastoma (14.6%). Odontogenic tumours were rarely detected in early childhood, and their prevalence increased with age. An almost equal distribution was observed with respect to sex and the site of the lesions. This study is the largest reported retrospective analysis describing odontogenic tumours in children and adolescents to date. The authors detected some variation in the relative frequency of odontogenic tumours compared with similar reports. Additional studies should be conducted based on the new WHO classification and predetermined age parameters to enable comparative analysis among different worldwide populations.