Definition of Familial eosinophilia

Familial eosinophilia: An autosomal dominant condition characterized by an abnormally high level of eosinophils in the blood. Despite the prolonged eosinophilia, there may be no symptoms. The gene for familial eosinophilia, called EOS, has been mapped to chromosome region 5q31-33 containing the cytokine gene cluster which includes the genes for interleukin-3 (IL-3), interleukin-5 (IL-5), and granulocyte colony-stimulating factor (G-CSF), and all of which are thought play roles in the development, proliferation, and activation of eosinophils.