What are the implications of mild absolute eosinophilia (Eosinophil Count) and mild absolute basophilia (Basophil Count)?

From the Guidelines

Mild absolute eosinophilia and mild absolute basophilia are generally not immediately life-threatening and typically require a thorough clinical evaluation to determine the underlying cause, rather than immediate treatment of the elevated cell counts themselves. These conditions often present with slightly elevated levels of eosinophils and basophils in the bloodstream, which can be indicative of various underlying conditions such as allergic reactions, parasitic infections, certain medications, autoimmune disorders, or some cancers 1. It is essential to note that the presence of eosinophilia, in particular, can be associated with eosinophilic oesophagitis (EoE), a condition where the esophagus becomes inflamed due to an allergic reaction or other causes, leading to symptoms like dysphagia and food impaction 1.

Key Considerations

• A detailed medical history is crucial, focusing on recent medication changes, travel history, and symptoms of allergies or infections.
• Additional testing may include stool examination for parasites, allergy testing (though its utility in guiding dietary elimination in EoE is questionable 1), and possibly bone marrow examination if blood disorders are suspected.
• Treatment should target the underlying cause rather than the laboratory finding itself. For instance, antiparasitic medications for parasitic infections, discontinuation of offending medications if drug-induced, or appropriate management of allergic conditions.
• In the context of EoE, the British Society of Gastroenterology and British Society of Paediatric Gastroenterology, Hepatology and Nutrition recommend commencing treatment with a single modality therapy of either diet or pharmacotherapy, reserving combination therapy for selected patients who fail monotherapy 1.

Management Approach

• For patients with EoE, a multiprofessional team approach is recommended, including an experienced clinician, a specialist dietitian, and for selected patients, an allergist 1.
• The role of allergy testing in guiding dietary elimination for EoE is not recommended due to low efficacy and the consideration that EoE is primarily a non-IgE-mediated condition 1.
• Exclusive elemental diets have a limited role in eosinophilic oesophagitis, with high efficacy but low concordance rates, and should be reserved for patients refractory to other treatments 1.

Conclusion on Approach

Given the information and the need to prioritize morbidity, mortality, and quality of life, a thorough diagnostic workup and treatment of the underlying cause, rather than the eosinophilia or basophilia itself, is the recommended approach. This ensures that the root cause of the elevated cell counts is addressed, potentially improving outcomes and quality of life for the patient.

From the Research

Implications of Mild Absolute Eosinophilia and Mild Absolute Basophilia

• Mild absolute eosinophilia is generally defined as a peripheral blood eosinophil count less than 1.5 × 10^9/L 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
• The goal of therapy is to mitigate eosinophil-mediated organ damage, and corticosteroids are first-line therapy for patients with lymphocyte-variant hypereosinophilia and idiopathic hypereosinophilic syndrome (HES) 2, 3, 4
• Basophilia is a rare disorder of the complete blood count (CBC) and its management in daily practice remains unclear 5
• The association between basophilia and myeloid neoplasm, especially chronic myeloid neoplasm, is well established, and a practical approach to manage basophilia includes checking the real existence of the basophilia, looking for symptoms that suggest reactive basophilia, and deciding which examinations need to be prescribed to confirm a neoplastic basophilia 5
• There is limited information available on the implications of mild absolute basophilia, and further research is needed to fully understand its effects and appropriate management 5

Diagnosis and Management

• Diagnostic evaluation of primary eosinophilias relies on a combination of various tests, including morphologic review of the blood and marrow, standard cytogenetics, fluorescence in situ hybridization, molecular testing, and flow immunophenotyping 2, 3, 4
• Disease prognosis relies on identifying the subtype of eosinophilia, and a semi-molecular classification scheme of disease subtypes is endorsed by the World Health Organization 2, 3, 4
• For basophilia, a practical approach includes checking the real existence of the basophilia, looking for symptoms that suggest reactive basophilia, and deciding which examinations need to be prescribed to confirm a neoplastic basophilia 5

Treatment Options

• Corticosteroids are first-line therapy for patients with lymphocyte-variant hypereosinophilia and idiopathic hypereosinophilic syndrome (HES) 2, 3, 4
• Hydroxyurea and interferon-α have demonstrated efficacy as initial treatment and in steroid-refractory cases of HES 2, 3, 4
• Mepolizumab, an interleukin-5 (IL-5) antagonist monoclonal antibody, is approved by the U.S Food and Drug Administration for patients with idiopathic HES 2, 4
• Targeted therapies such as the IL-5 receptor antibody benralizumab, IL-5 monoclonal antibody depemokimab, and various tyrosine kinase inhibitors are under active investigation 4