From the Guidelines
Peripheral blood eosinophilia is defined as an absolute eosinophil count greater than 0.5 x 10^9/L in blood, according to the most recent and highest quality study 1.
Definition and Classification
Peripheral blood eosinophilia refers to an abnormally high level of eosinophils, a type of white blood cell, in the peripheral blood. This condition occurs when the body produces more eosinophils in response to various triggers. Eosinophils play a role in fighting parasitic infections and are involved in allergic reactions and inflammatory processes.
Causes and Management
Common causes of peripheral blood eosinophilia include:
- Allergic disorders (such as asthma, hay fever, drug allergies)
- Parasitic infections
- Certain medications
- Autoimmune disorders
- Hematologic malignancies The management of peripheral blood eosinophilia depends on identifying and treating the underlying cause. Persistent unexplained eosinophilia warrants further investigation as it may indicate a more serious condition requiring specific treatment.
Key Points
- Eosinophilia can be classified as mild, moderate, or severe based on the absolute eosinophil count.
- Hypereosinophilia (HE) is defined as persistent elevated eosinophil count ≥1.5 x 10^9/L in blood and/or tissue.
- The classification and definition of HE and related syndromes have been proposed by an international consensus proposal, which includes hereditary (familial), primary (clonal/neoplastic), secondary (reactive), and HE of undetermined significance variants 1.
- The management of HE and related syndromes depends on the underlying cause and may involve targeted therapies, such as imatinib for patients with PDGFRA rearrangement 1.
From the Research
Definition of Peripheral Blood Eosinophilia
- Peripheral blood eosinophilia is defined as an absolute count of > 500 eosinophils per mm3 of peripheral blood 2
- It can also be defined as a peripheral blood eosinophil count greater than 1.0 × 10^9 /L 3 or 1.5 × 10^9 /L 4
- Eosinophilia is associated with many disorders, limiting its usefulness as a diagnostic tool in screening for parasite infections 2
Causes of Peripheral Blood Eosinophilia
- Fungal allergy, parasitic infection, and severe eosinophilic asthma are common causes of peripheral blood eosinophilia 3
- Hypereosinophilic syndrome (HES) disease, including eosinophilic granulomatosis with polyangiitis (EGPA), is a less common cause 3
- Other causes include myeloproliferative disease, lymphocyte-variant hypereosinophilic syndrome, and idiopathic hypereosinophilic syndrome 4
Diagnosis and Management
- Diagnosis of peripheral blood eosinophilia relies on morphologic review of the blood and marrow, standard cytogenetics, fluorescence in situ hybridization, next generation sequencing gene assays, and flow immunophenotyping 4
- A semi-structured algorithm can be used to determine the underlying diagnosis 3
- Treatment options include corticosteroids, hydroxyurea, interferon-α, and targeted therapies such as imatinib and mepolizumab 4