eosinopenia

Eosinopenia is a condition where the number of eosinophils, a type of white blood cell, in circulating blood is lower than normal. Eosinophils are a type of granulocyte and consequently from the same cellular lineage as neutrophils, basophils, and mast cells. Along with the other granulocytes, eosinophils are part of the innate immune system and contribute to the defense of the body from pathogens. The most widely understood function of eosinophils is in association with allergy and parasitic disease processes, though their functions in other pathologies are the subject of ongoing research. The opposite phenomenon, in which the number of eosinophils present in the blood is higher than normal, is known as eosinophilia.

== Definition and diagnosis == The definition of eosinopenia varies in clinical practice, and normal eosinophil levels vary among the population. One common definition is an absolute eosinophil count of less than 50 cells/μLiter of blood. Other definitions include less than 10 cells/μLiter, while some clinical laboratories classify 0 cells/μLiter as within the acceptable range. The diagnosis of eosinopenia is challenging due to the low number of eosinophils normally present in blood and the fluctuations in eosinophil levels throughout the day.