eosinophilia:

Patients with elevated eosinophil counts that do not have a known 
cause for this alteration, such as a parasitic infection or 
allergic disorder, were classified as having a hypereosinophilic 
syndrome of unknown cause. It is now understood that some have a 
leukemic basis for the eosinophil increase. Thus, some patients 
with high blood eosinophil counts have eosinophilic leukemia. The 
chronic form of eosinophilic leukemia is uncommon. The acute form 
is rare.