 This disorder is distinguished from 1) eosinophilia, which is an elevation in this count above normal levels of 0.5 x 109/L (i.e.500/μl) but below the hypereosinophilia cutoff level and 2) the hypereosinophilic syndrome, which is a sustained elevation in this count above 1.5 x 109/L (i.e.1,500/μl) that is also associated with evidence of eosinophil-based tissue injury.