From the Guidelines
A high absolute eosinophil count (EOS) is a medical condition that requires immediate attention, as it can indicate a range of underlying causes, including allergic reactions, parasitic infections, and inflammatory disorders, and can lead to significant end-organ damage if left untreated. According to the most recent and highest quality study, 1, hypereosinophilic syndromes (HES) are characterized by elevated eosinophils in the peripheral blood and organ/tissue damage due to eosinophilic infiltration. The study highlights the importance of distinguishing HES from other conditions, such as eosinophilic esophagitis, and notes that patients with HES often present with gastrointestinal symptoms.
Some key points to consider in the management of high EOS include:
- Identifying and treating the underlying cause of the eosinophilia, whether it be an allergic reaction, parasitic infection, or inflammatory disorder
- Using antihistamines, such as cetirizine (10mg daily) or loratadine (10mg daily), to manage allergic conditions
- Prescribing corticosteroids, such as prednisone (starting at 20-40mg daily with tapering), for more severe cases or those associated with organ damage
- Using specific antiparasitic medications, such as albendazole (400mg twice daily for 3-5 days) or ivermectin (single dose based on weight), to treat parasitic infections
- Conducting comprehensive evaluations, including stool examinations for parasites, allergy testing, and possibly chest imaging, to determine the underlying cause of the eosinophilia
It is also important to note that long-standing moderate/high-grade eosinophilia (>1.5 x 10^9/L) can itself result in significant end-organ damage, as highlighted in the study by 1. Therefore, prompt and effective management of high EOS is crucial to prevent long-term complications. The study by 1 provides a comprehensive overview of the classification and diagnosis of hypereosinophilic syndromes, and notes that myeloid/lymphoid neoplasms with eosinophilia can be associated with a range of tyrosine kinase fusion genes.
From the Research
Definition and Causes of High EOS
- High EOS (eosinophilia) is generally defined as a peripheral blood eosinophil count greater than 1500/mm3 2
- Eosinophilia can be associated with tissue damage and may be caused by a variety of factors, including atopy/allergic reactions, drug reactions, parasitic infections, and paraneoplastic syndromes 3
- Hypereosinophilia can also be related to hematological malignancies, and it is essential to be aware of the potential for secondary organ damage, such as in the case of hypereosinophilic syndrome 3
Diagnosis and Evaluation
- 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 2
- The 2016 World Health Organization endorses a semi-molecular classification scheme of disease subtypes, which includes the major category "myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2" 2
- Lymphocyte-variant hypereosinophilia is an aberrant T-cell clone-driven reactive eosinophilia, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion 2
Treatment Options
- The goal of therapy is to mitigate eosinophil-mediated organ damage, and treatment options vary depending on the underlying cause and severity of the eosinophilia 2
- 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
- Corticosteroids are first-line therapy for patients with lymphocyte-variant hypereosinophilia and HES, while hydroxyurea and interferon-alpha have demonstrated efficacy as initial treatment and steroid-refractory cases of HES 2, 4
- The use of antibodies against interleukin-5 (IL-5) and other targets on eosinophils remains an active area of investigation 2