From the Guidelines
Eosinophilia is most commonly caused by allergic disorders, such as asthma, hay fever, drug allergies, and atopic dermatitis, which account for approximately 80% of cases, as well as parasitic infections, particularly those involving tissue-invasive helminths like Strongyloides, Ascaris, hookworm, and Schistosoma 1. The causes of eosinophilia can be broadly categorized into several groups, including:
- Allergic disorders, such as allergic asthma, food allergy, atopic dermatitis, and drug reactions, which are the most common cause of secondary (reactive) eosinophilia 1
- Parasitic infections, particularly those involving tissue-invasive helminths like Strongyloides, Ascaris, hookworm, and Schistosoma, which are a significant cause of eosinophilia, especially in returning travelers and migrants 1
- Immunodeficiency syndromes, such as hyperimmunoglobulin E syndrome, Omenn syndrome, and Wiskott-Aldrich syndrome, which can be associated with abnormal immunoglobulin levels and eosinophilia 1
- Hematologic disorders, including hypereosinophilic syndrome, mastocytosis, and some lymphomas and leukemias, which can cause marked eosinophilia 1
- Solid tumors, particularly those of the lung, gastrointestinal tract, and genitourinary system, which may induce paraneoplastic eosinophilia 1 It is essential to consider the patient's travel history, medication use, and presence of any systemic symptoms to determine the underlying cause of eosinophilia, as persistent eosinophilia can cause significant end-organ damage, particularly affecting the heart, lungs, and central nervous system 1. In patients with eosinophilia, it is crucial to rule out secondary (reactive) causes, such as allergic disorders and parasitic infections, and to consider referral to a hematologist for further investigations if no cause can be identified or if there is evidence of end-organ damage 1.
From the Research
Causes of Eosinophilia
Eosinophilia can be caused by a variety of diseases, including:
- Allergies
- Autoimmune diseases
- Vasculitides
- Dermatoses
- Malignancies
- Drug-induced side effects
- Parasitic and non-parasitic infections 2, 3, 4
Parasitic Infections
Parasitic infections are a common cause of eosinophilia, particularly in patients returning from the tropics 2, 5. The most frequent causes of eosinophilia in these patients are:
- Helminthic parasites
- Intestinal parasites
Non-Parasitic Infections
Non-parasitic infections can also cause eosinophilia, including:
- Cryptococcosis
- Endemic systemic mycoses (coccidioidomycosis, histoplasmosis)
- Invasive mould infections (Aspergillus fumigatus, Mucor spp.) 2
Malignancies
Eosinophilia can also be associated with various types of cancer, including:
- Hematologic tumors (Hodgkin's disease, lymphomas)
- Solid tumors (colon, cervix, lung, breast, ovary) 6
Diagnostic Approach
The diagnostic approach to eosinophilia includes: