Eosinophils are white blood cells that participate in immunologic and allergic events. Common causes of eosinophilia are listed in Table 2. The relative frequency of each cause usually relates to the clinical setting.
For example, parasitic infections are often responsible for eosinophilia in pediatric patients, and drug reactions commonly cause an increased eosinophil count in hospitalized patients. Dermatologists frequently find eosinophilia in patients with skin rashes, and pulmonologists often see elevated numbers of eosinophils in conjunction with pulmonary infiltrates and bronchoallergic reactions.
Table 2 -Etiology of Eosinophilia
Infections: scarlet fever, chorea, leprosy, genitourinary infections
Immunologic disorders: rheumatoid rthritis, periarteritis, lupus erythematosus, eosinophilia-myalgia syndrome
Pleural and pulmonary conditions: Löffler’s syndrome, pulmonary infiltrates and eosinophilia
Malignancies: non-Hodgkin’s lymhoma, Hodgkin’s disease
Myeloproliferative disorders: chronic myelo-genous leukemia, polycythemia vera, myelofibrosis
Adrenal insufficiency: Addison’s isease
Table 3 - Etiology of Basophilia
Infections: viral infections (varicella), chronic sinusitis
Inflammatory conditions: inflammatory bowel disease, chronic airway inflammation, chronic dermatitis
Myeloproliferative disorders: chronic myelogenous leukemia, polycythemia vera, myelofibrosis
Alteration of marrow and reticuloendothelial compartments: chronic hemolytic anemia, Hodgkin’s disease, splenectomy
Endocrinologic causes: hypothyroidism, ovulation, estrogens
Other causes of eosinophilia include malignancies, especially those affecting the immune system (Hodgkin’s disease and non-Hodgkin’s lymphoma), and immunologic disorders such as rheumatoid arthritis and periarteritis. Eosinophilia-myalgia syndrome, a disorder associated with dietary supplements of tryptophan, resembles a connective tissue disease with fibrosis of muscle fascial tissue and peripheral eosinophilia.