What is the appropriate workup and management for eosinophilia (Eosinophilia is a condition characterized by an elevated eosinophil count)?

From the Guidelines

Eosinophilia workup and management should prioritize a thorough history, physical examination, and first-line laboratory tests, followed by targeted treatment based on the underlying cause, with a focus on reducing morbidity, mortality, and improving quality of life. The initial evaluation should include confirming persistent elevation of eosinophils above 500 cells/μL through repeat testing, a thorough history focusing on travel, medications, allergies, and symptoms of organ involvement, and a complete physical examination 1. First-line laboratory tests include complete blood count with differential, comprehensive metabolic panel, urinalysis, and stool examination for ova and parasites. Depending on clinical suspicion, additional testing may include serum IgE levels, ANCA, specific parasite serologies, chest imaging, and pulmonary function tests.

For eosinophilic oesophagitis (EoE), the recommended initial treatment is a single modality therapy of either diet or pharmacotherapy, with pharmacotherapy being easier to implement than dietary restriction 1. The British Society of Gastroenterology (BSG) and British Society of Paediatric Gastroenterology, Hepatology and Nutrition (BSPGHAN) joint consensus guidelines recommend commencing treatment with a single modality therapy, reserving combination therapy for selected patients who fail monotherapy and have access to a multiprofessional team including a dietitian to follow them up and monitor response carefully. Allergy testing to foods is not recommended for choosing the type of dietary restriction therapy for EoE, as it has been found to be no more effective than empirical dietary elimination 1.

In terms of specific treatments, swallowed steroids and topical corticosteroids have been shown to be effective in reducing symptoms and improving histological remission rates in EoE 1. A retrospective cohort study of 29 children found that a 3-month trial of swallowed steroids and a trial of food elimination diet (TFED) was effective in reducing median eosinophil counts and improving dysphagia. Similarly, a study in 23 adults reported that combination therapy with topical corticosteroids and an elimination diet improved overall symptoms in 88% of patients.

For hypereosinophilic syndrome, first-line therapy is prednisone at 1 mg/kg/day with gradual taper based on response 1. The diagnosis of hypereosinophilic syndrome is made in the presence of eosinophils >1500/μL, and evaluation for secondary causes is essential, followed by treatment of the offending agent. Corticosteroid therapy is generally considered primary therapy for eosinophilic myocarditis, but its efficacy is not well supported.

Regular monitoring of eosinophil counts and organ function is essential during treatment, as persistent eosinophilia can lead to tissue fibrosis and permanent organ dysfunction through release of cytotoxic granule proteins. The urgency of workup and treatment intensifies with higher eosinophil counts and evidence of end-organ damage.

Key points to consider in eosinophilia workup and management include:

• Confirming persistent elevation of eosinophils above 500 cells/μL through repeat testing
• Thorough history and physical examination
• First-line laboratory tests, including complete blood count with differential, comprehensive metabolic panel, urinalysis, and stool examination for ova and parasites
• Targeted treatment based on the underlying cause
• Reducing morbidity, mortality, and improving quality of life
• Reserving combination therapy for selected patients who fail monotherapy and have access to a multiprofessional team
• Not recommending allergy testing to foods for choosing the type of dietary restriction therapy for EoE.

From the Research

Eosinophilia Workup

• The workup for eosinophilia involves excluding secondary causes of eosinophilia and evaluating for primary eosinophilias through 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," and the "MPN subtype, chronic eosinophilic leukemia, not otherwise specified" (CEL, NOS) 2.

Eosinophilia Management

• The goal of therapy is to mitigate eosinophil-mediated organ damage 3, 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 2.
• Hydroxyurea and interferon-alpha have demonstrated efficacy as initial treatment and steroid-refractory cases of HES 4, 2.
• Tyrosine kinase inhibitors, such as imatinib, have a central role in the treatment of hypereosinophilic syndromes, particularly in patients with a primary myeloid disorder or FIP1L1-PDGFRa positive cases 3, 4, 5.
• Eosinophil-targeted biotherapeutics, such as monoclonal antibodies against interleukin-5, interleukin-5Rα, IgE, and CD52, offer a promising area of research for the treatment of HES 3, 6, 2.