From the Guidelines
Elevated eosinophils and platelets can indicate a range of underlying conditions, and a definitive diagnosis requires a comprehensive evaluation, including a complete blood count with differential, peripheral blood smear, and possibly bone marrow examination, as outlined in the NCCN clinical practice guidelines 1. The presence of both elevated eosinophil and platelet counts may suggest conditions such as hypereosinophilic syndrome, certain cancers, or inflammatory disorders. According to the guidelines, hypereosinophilia is defined as ≥1.5 x 10^9/L eosinophils in the blood on two examinations, with an interval of at least one month, and/or tissue hypereosinophilia defined by specific criteria 1.
The diagnostic workup should aim to classify the eosinophilia into one of the following categories: primary (clonal/neoplastic), secondary (reactive), hereditary (familial), or hypereosinophilia of undetermined significance 1. The treatment approach will depend on the underlying cause, and it is crucial to identify and address the root cause rather than just managing the laboratory abnormalities. In some cases, evolving life-threatening end-organ damage may require immediate diagnosis and therapy, even in the absence of validated quantitative criteria for tissue hypereosinophilia 1.
Key considerations in the evaluation of elevated eosinophils and platelets include:
- Complete blood count with differential to confirm the elevation of eosinophils and platelets
- Peripheral blood smear to evaluate for any abnormal cell morphology
- Inflammatory markers to assess for underlying inflammation or infection
- Bone marrow examination, if clinically indicated, to evaluate for myeloid or stem cell neoplasms
- Molecular testing, if applicable, to identify specific genetic mutations associated with clonal eosinophilia, such as PDGFR or FGFR mutations 1.
Ultimately, a thorough diagnostic workup and clinical evaluation are essential to determine the underlying cause of elevated eosinophils and platelets and to guide appropriate treatment.
From the Research
Elevated Eosinophils and Platelets
Elevated eosinophils can be associated with various conditions, including:
- Parasitic diseases
- Allergic diseases
- Autoimmune diseases
- Connective tissue diseases
- Rheumatologic diseases
- Primary eosinophilia, such as hypereosinophilic syndrome
- Malignant states 2 Eosinophilia is defined as an elevation of eosinophils in the bloodstream, typically above 450-550 cells/μL 2.
Diagnosis and Classification
The diagnosis of eosinophilic disorders involves excluding secondary causes of eosinophilia and evaluating primary eosinophilias through morphologic review of blood and marrow, standard cytogenetics, fluorescence in situ hybridization, next-generation sequencing gene assays, and flow immunophenotyping 3. The 2016 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 myeloproliferative neoplasm subtype, chronic eosinophilic leukemia, not otherwise specified (CEL, NOS) 3.
Treatment and Management
Treatment of eosinophilic diseases has traditionally involved nonspecific eosinophil attenuation using glucocorticoids 4. However, novel biologic therapies targeting eosinophil maturation factors, such as interleukin (IL)-5 and the IL-5 receptor or IL-4/IL-13, have recently been approved for clinical use 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 3. Identification of rearranged PDGFRA or PDGFRB is critical due to the exquisite responsiveness of these diseases to imatinib 3.
Role of Eosinophils in Health and Disease
Eosinophils play a homeostatic role in the body's immune responses, involved in combating some parasitic, bacterial, and viral infections and certain cancers, and have pathologic roles in diseases including asthma, chronic rhinosinusitis with nasal polyps, eosinophilic gastrointestinal disorders, and hypereosinophilic syndromes 4. New research has shown that eosinophils are also involved in several homeostatic processes, including metabolism, tissue remodeling and development, neuronal regulation, epithelial and microbiome regulation, and immunoregulation, indicating that these cells may play a crucial role in metabolic regulation and organ function in healthy humans 4.