From the Guidelines
Elevated absolute eosinophil count is most commonly caused by allergic reactions, parasitic infections, and inflammatory conditions, with allergic disorders being the most common cause, occurring in about 80% of cases, as noted in the study by 1. The causes of elevated eosinophils can be broadly categorized into several groups, including:
- Allergic reactions, such as allergic asthma, food allergy, atopic dermatitis, and drug reactions, which are the most common cause of secondary (reactive) eosinophilia, as stated in the study by 1
- Parasitic infections, such as strongyloidiasis due to Strongyloides stercoralis exposure, which is generally the most common parasitic infection, as mentioned in the study by 1
- Inflammatory and autoimmune conditions, such as eosinophilic esophagitis, asthma, eczema, and certain vasculitides, which frequently present with elevated eosinophils, as noted in the study by 1
- Certain cancers, such as lymphomas and leukemias, which can also cause elevated eosinophils, as mentioned in the study by 1
- Hypereosinophilic syndrome, which is a rare and heterogeneous group of syndromes characterized by elevated eosinophils in the peripheral blood and organ/tissue damage due to eosinophilic infiltration, as described in the study by 1 It is essential to determine the underlying cause of elevated eosinophils, as the treatment plan will depend on the specific cause, as emphasized in the study by 1. Further work-up and consultation with allergy/immunology may be necessary to guide diagnostic work-up and treatment, as recommended in the study by 1.
From the Research
Causes of Elevated Eosinophils Absolute
- Eosinophilic immune dysfunction, which appears central to exacerbation pathogenesis and disease control in severe asthma, may be involved in the aetiology of other eosinophil-related conditions, including chronic obstructive pulmonary disease, chronic rhinosinusitis with nasal polyposis, eosinophilic granulomatosis with polyangiitis, and hypereosinophilic syndrome 2
- Hypereosinophilia, defined as a peripheral blood eosinophil count greater than 1.5 × 109 /L, can be caused by a range of nonhematologic (secondary or reactive) and hematologic (primary or clonal) disorders, including myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1, chronic eosinophilic leukemia, lymphocyte-variant hypereosinophilic syndrome, and idiopathic hypereosinophilic syndrome 3
- Eosinophilic skin diseases, characterized by eosinophil infiltration and/or degranulation in skin lesions, can be caused by allergic reactions, parasitic infestations, arthropod bites, autoimmune blistering skin diseases, and rare types of eosinophilic dermatoses with unknown origin, such as eosinophilic cellulitis, granuloma faciale, and eosinophilic pustular folliculitis 4, 5
- Eosinophils can also contribute to autoimmune diseases, including inflammatory bowel diseases, neuromyelitis optica, bullous pemphigoid, autoimmune myocarditis, primary biliary cirrhosis, and eosinophilic granulomatosis with polyangiitis, through mechanisms such as degranulation of cytotoxic granule proteins, induction of antibody-dependent cell-mediated cytotoxicity, and release of proteases degrading extracellular matrix 6
Eosinophil-Related Conditions
- Chronic obstructive pulmonary disease
- Chronic rhinosinusitis with nasal polyposis
- Eosinophilic granulomatosis with polyangiitis
- Hypereosinophilic syndrome
- Inflammatory bowel diseases
- Neuromyelitis optica
- Bullous pemphigoid
- Autoimmune myocarditis
- Primary biliary cirrhosis
- Eosinophilic cellulitis
- Granuloma faciale
- Eosinophilic pustular folliculitis
Diagnostic Evaluation
- Morphologic review of the blood and marrow
- Standard cytogenetics
- Fluorescence in situ hybridization
- Next generation sequencing gene assays
- Flow immunophenotyping
- Identification of rearranged PDGFRA or PDGFRB 3