From the Guidelines
Elevated eosinophils, or eosinophilia, should be promptly evaluated by a healthcare provider to determine the underlying cause, as persistent untreated eosinophilia can lead to significant end-organ damage and impact quality of life. This condition occurs when eosinophil levels exceed 0.45 x 10^9/L 1. Common causes include allergic reactions, parasitic infections, certain medications, autoimmune disorders, and some cancers. If you have elevated eosinophils, your doctor will likely order additional tests such as:
- A complete blood count with differential
- Stool examination for parasites
- Allergy testing
- Chest imaging Treatment depends on the underlying cause - for parasitic infections, antiparasitic medications like albendazole (400 mg twice daily for 3-5 days) or ivermectin (200 mcg/kg as a single dose) may be prescribed 1. For allergic conditions, antihistamines, corticosteroids, or biologics targeting IL-5 (like mepolizumab) might be used. Severe cases with organ damage may require systemic corticosteroids like prednisone (40-60 mg daily, tapered over weeks). According to the most recent guidelines, the diagnosis and management of eosinophilic oesophagitis, a condition characterized by eosinophil-predominant mucosal inflammation, should be based on a peak eosinophil count of ≥15 eosinophils/high power field (or ≥15 eosinophils/0.3 mm² or >60 eosinophils/mm²) 1. Eosinophils are white blood cells that play a role in immune response, particularly against parasites and in allergic reactions, by releasing inflammatory mediators. Identifying and addressing the underlying cause of eosinophilia is essential to prevent long-term health problems, such as those associated with Strongyloides stercoralis infection in immunocompromised individuals 1.
From the Research
Definition and Diagnosis of Elevated Eosinophils
- Elevated eosinophils, also known as hypereosinophilia, is generally defined as a peripheral blood eosinophil count greater than 1500/mm^3 or 1.5 × 10^9/L, and may be associated with tissue damage 2, 3, 4.
- The diagnostic evaluation of primary eosinophilias relies on a combination of morphologic review of the blood and marrow, standard cytogenetics, fluorescent in situ hybridization, flow immunocytometry, and T-cell clonality assessment to detect histopathologic or clonal evidence for an acute or chronic myeloid or lymphoproliferative disorder 2, 3, 4.
Classification and Subtypes of Eosinophilic Disorders
- The World Health Organization endorses a semi-molecular classification scheme of disease subtypes, including "myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2", and the "MPN subtype, chronic eosinophilic leukemia, not otherwise specified" (CEL, NOS) 2, 4.
- Lymphocyte-variant hypereosinophilia is an aberrant T-cell clone-driven reactive eosinophilia, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion 2, 4.
Treatment Options for Eosinophilic Disorders
- The goal of therapy is to mitigate eosinophil-mediated organ damage 2, 3, 4.
- For patients with milder forms of eosinophilia without symptoms or signs of organ involvement, a watch and wait approach with close-follow-up may be undertaken 2, 3, 4.
- Corticosteroids are first-line therapy for patients with lymphocyte-variant hypereosinophilia and HES 2, 3, 4.
- Hydroxyurea and interferon-alpha have demonstrated efficacy as initial treatment and in steroid-refractory cases of HES 2, 3, 5, 4.
- The use of antibodies against interleukin-5 (IL-5) and other targets on eosinophils remains an active area of investigation 2, 3, 4.