From the Guidelines
Eosinophilia is primarily caused by helminth infections, allergic disorders, and hematologic malignancies.
Causes of Eosinophilia
- Infectious causes: Helminth infections, such as Strongyloides stercoralis and Schistosomiasis, are common causes of eosinophilia in returning travelers and migrants from the tropics 1.
- Non-infectious causes: Allergic disorders, such as asthma, atopic dermatitis, and drug reactions, are the most common cause of secondary (reactive) eosinophilia 1.
- Hematologic malignancies: Myeloid/lymphoid neoplasms with eosinophilia, such as Hypereosinophilic syndrome (HES), can also cause eosinophilia 1.
Key Points
- Eosinophilia can be defined as a peripheral blood eosinophil count of >0.45 x 10^9/L 1.
- Concentrated stool microscopy and strongyloides serology should be performed on all patients with eosinophilia, regardless of geographic exposure 1.
- Empiric treatment with an antihelminthic agent, such as albendazole, may be considered in the absence of a specific diagnosis 1.
From the Research
Causes of Eosinophilia
The causes of eosinophilia are diverse and can be categorized into several groups, including:
- Allergic diseases, such as atopic disease 2
- Infectious diseases, including parasitic infections, such as helminthic infections 3, 2
- Autoimmune and rheumatologic diseases 4, 5
- Malignant diseases, including myeloproliferative disorders and chronic eosinophilic leukemia 3, 6
- Primary eosinophilia, such as hypereosinophilic syndrome 4, 3
- Connective tissue diseases and other rare idiopathic disorders 5
Specific Causes
Some specific causes of eosinophilia include:
- Parasitic infections, which can cause severe eosinophilia with eosinophil counts >5000/µl 3
- Malignancies, which were found to be the most common cause of hypereosinophilia in one study 6
- Allergies and skin diseases, which can also cause hypereosinophilia 6
- Bone marrow clonal diseases, such as chronic eosinophilic leukemia 6
- Hepatobiliary diseases and infectious diseases, which can also contribute to eosinophilia 6
Diagnosis and Classification
Eosinophilia can be classified based on the absolute number of eosinophils in the peripheral blood or tissue, and the grade of eosinophilia 3. Hypereosinophilic syndrome is defined as eosinophilia with >1500 eosinophils/µl and a duration of more than 6 months, with exclusion of parasitic infections, allergies, or other causes of tissue eosinophilia with end-organ damage 3. A detailed medical history, physical examination, and laboratory analyses, including bone marrow investigations, are necessary for the diagnosis of persistent eosinophilia 3.