Reactive (secondary):
- Drug reactions
- Allergy/hypersensitivity reaction
- Infections (especially tissue-invasive parasites, such as strongyloides)
- Cancer
- Sarcoidosis
- Connective tissue diseases
- Adrenal insufficiency
- Pulmonary diseases such as eosinophilia pneumonia
Clonal (primary):
- Chronic eosinophilic leukemia
- Myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1, or with PCM1-JAK2
- Other acute and chronic primary bone marrow processes such as myeloproliferative neoplasms