Eosinophilia occurs when the eosinophil count is over >0.04 x 109/L. The differential diagnosis of eosinophilia is broad. Often mild eosinophilia persists over longer periods, but no cause etiology can be found and no symptoms occur. Cases in which values of  > 1.5 x 109/L persist, and a cause cannot be established, are referred to as idiopathic eosinophilia syndromes.


Clinical picture:
Eosinophilia is not a disease. The clinical picture is dependent on the underlying disease. In distinct eosinophilia, organs can incur damages due to tissue infiltration and/or The release of eosinophilic substances such as cytokines, enzymes and other proteins. Especially feared is cardiomyopathy and damages to heart valves, which can occasionally be life-threatining. Unfortunately, it is impossible to predict if organ damages occur or not.


Differential diagnosis of eosinophilia:

  1. Primary eosinophilia (diseases of the hematopoietic precursor cell)
    1. Chronic eosinophilic leukemia (CEL)
    2. Chronic myelomonocytic leukemia with eosinophilia (CMML eos)
    3. Chronic myeloid leukemia (CML)
    4. Acute leukemias (e.g. acute myelomonocytic leukemia with eosinophilia)
    5. Systemic mastocytosis
  2. Secondary eosinophilia (within an comorbidity)
    1. Infections with parasites (echinococci, Strongyloides stercoralis, Hook worms, filaria, Toxocara canis)
    2. Fungi (bronchopulmonary aspergillosis, Coccidioidomycosis)
    3. Viruses (HIV, HTLV-1/2)
    4. Allergic diseases (asthma, rhinitis, atopic dermatitis)
    5. Rheumatoid diseases
    6. Churg-Strauss-syndrome
    7. Hematologic neoplasm (Hodgkin lymphoma, mature cell lymphatic neoplasms (lymphoma) of B- and T-cells, acute lymphoblastic leukemias)
    8. Solid neoplasms
    9. Eosinophilia with organ specific involvement
    10. Drugs
    11. Transplant rejection
    12. Cholesterol embolism
    13. Morbus Addison
  3. Hypereosinophilic syndrome (HES)



Eosinophilia is usually mild. However, under certain circumstances it can become quite marked and achieve values of 20 - 40 x 109/L.. The eosinophilic granulocytes are mostly morphologically normal.