Hyperimmunoglobulinemia E in the Absence of Atopy and Filarial Infection: The Huaorani of Ecuador

Abstract

Hyperimmunoglobulinemia E (HIGE) is associated with various conditions such as atopy, dermatitis, hypersensitivity reactions, and certain parasitic infections. In the course of vaccination initiatives in the province of Napo, eastern Ecuador, blood samples were collected from one of the two remaining rural subgroups of Huaorani Indians who in 1979 were reported to have the world's highest concentrations of IgE. One subgroup of Huaorani, the Dicaron, lives in a protected Amazonian region which has reportedly suffered from extensive pollution after petroleum industry exploration. Plasma was collected from 31 members of the Dicaron (age range 15-75 years), eight non-Dicaron Huaorani, and 16 Quichua Indians from the same province, and tested for IgE, IgG, IgM, IgA, and immunoglobulin allotypes. Subjects were examined for evidence of filariasis, a group of parasitic diseases associated with HIGE. Mean IgE concentration in the Dicaron was measured by CAP ELISA at 11,850 IU/mL (range 5000-33,000) while IgA and IgM concentrations were within normal limits compared to North American controls. IgG levels were slightly elevated and there was no evidence of filariasis. Compared to the Quichua and non-Dicaron Huaorani, two other Amerindian tribes in the Ecuadorian Amazon, the highest concentrations of IgE were recorded from the Dicaron who live within the allegedly polluted section of the Amazon. We conclude that an unexplained HIGE syndrome exists among only one subgroup of Huaorani, the Dicaron. Other eastern Ecuadorian Amerindians, such as the Quichua and resettled Huaorani, have IgE concentrations expected in a population with intestinal helminthiasis. Environmental factors cannot be excluded as the cause of HIGE in the Dicaron.