Hypereosinophilia

Hypereosinophilia or hypereosinophilic syndrome is a disease characterised by a marked increase in the eosinophil count in the bloodstream.

The eosinophil count in human blood is normally 0.4 × 10/L (0.1 - 0.6) and results from a balance between production of eosinophils and emigration through post-capillary venules (Yamaguchi et al. 1991). Eosinophils are only a small minority of peripheral blood leucocytes and in normal subjects, most are found in the tissues of the lung and gastro-intestinal tract (Beeken et al. 1987). Blood eosinophil counts are arbitrarily classified as mild - between 0.6 to 1.5 × 10/L; moderate between 1.5 to 5 × 10/L and severe when greater than 5 × 10/L.