What are the diagnostic and treatment approaches for eosinophilic pneumonia and hypereosinophilic syndrome?

From the Guidelines

Diagnosing and treating eosinophilic pneumonia and hypereosinophilic syndrome requires a comprehensive approach, including clinical evaluation, laboratory testing, imaging, and often tissue sampling, with a focus on minimizing morbidity, mortality, and improving quality of life. The diagnostic work-up for these conditions involves a range of investigations, including routine laboratory tests, immunological and allergic tests, infectious tests, and imaging studies, as outlined in the 2023 evidence-based guideline for the diagnosis and management of eosinophilic granulomatosis with polyangiitis 1.

Key Diagnostic Tests

• Chest imaging (CT scan) to identify peripheral infiltrates
• Bronchoalveolar lavage to demonstrate increased eosinophils (>25%)
• Peripheral blood eosinophilia (>500 cells/μL)
• Lung biopsy in some cases
• For hypereosinophilic syndrome, diagnosis requires persistent eosinophilia (>1,500 cells/μL) for at least six months with evidence of end-organ damage, after excluding secondary causes

Treatment Approaches

• Corticosteroids, such as prednisone, are the primary treatment, with a typical starting dose of 0.5-1 mg/kg/day for 2-4 weeks, followed by a gradual taper over 2-6 months depending on response 1
• Acute severe cases may require methylprednisolone 125-250 mg IV every 6 hours initially
• For steroid-resistant or dependent cases, second-line agents include hydroxyurea, interferon-alpha, or targeted therapies like mepolizumab or benralizumab
• Hypereosinophilic syndrome with FIP1L1-PDGFRA gene rearrangement responds well to imatinib

Monitoring Treatment Efficacy

• Symptom improvement
• Eosinophil count normalization
• Resolution of radiographic abnormalities
• The goal of treatment is to prevent permanent organ damage from eosinophilic infiltration and inflammation, and to improve quality of life, as emphasized in the european position paper on rhinosinusitis and nasal polyps 2020 1.

Comprehensive Disease Assessment

• The Birmingham Vasculitis Activity Score (BVAS) is commonly used to assess disease activity, but it has limitations in evaluating asthma and ENT disease
• Disease scores that specifically address asthma and ENT disease, such as the Asthma Control Questionnaire or the 22-item Sino-Nasal Outcome Test, can be combined with the BVAS for a more comprehensive disease assessment in patients with EGPA 1.

From the Research

Diagnostic Approaches

• Eosinophilic lung diseases are diagnosed based on a combination of clinical, radiologic, and pathologic findings 2
• The percentages of eosinophils in peripheral blood and bronchoalveolar lavage fluid are essential parts of the evaluation 2
• Chest computed tomography (CT) demonstrates a more characteristic pattern and distribution of parenchymal opacities than does conventional chest radiography 2
• Radiographic evidence of pulmonary disease, histopathologic evidence of tissue eosinophilia, and increased eosinophils in BAL fluid are used to support the diagnosis of eosinophilia with pulmonary involvement 3

Treatment Approaches

• Prednisone, hydroxyurea, and interferon alpha 2b are effective treatments for hypereosinophilic syndromes, and their use in combination can control eosinophilia in most patients 4
• Corticosteroids are the mainstay of treatment for many eosinophilic pneumonias, particularly for acute and chronic eosinophilic pneumonias 5
• Eosinophil-directed interventions, including biologic therapies, are increasingly being used to manage eosinophilic lung disease presentations 3
• Treatment strategies are directed at the underlying cause when identifiable, and the urgency of treatment may be guided by the presence of severe end-organ involvement or life-threatening complications 3

Eosinophilic Pneumonias and Hypereosinophilic Syndrome

• Eosinophilic pneumonias are a heterogeneous group of diseases characterized by an increase in eosinophils in lung tissue or bronchoalveolar lavage fluid 5
• Hypereosinophilic syndromes are characterized by an increased number of eosinophils in peripheral blood, lung tissue, sputum, or bronchoalveolar lavage fluid, and can have systemic manifestations 6
• Acute eosinophilic pneumonia, chronic eosinophilic pneumonia, and idiopathic hypereosinophilic syndrome are examples of eosinophilic lung diseases of unknown cause 2
• Early and accurate diagnosis is imperative in certain diseases, such as acute eosinophilic pneumonia, as delayed diagnosis and treatment can lead to fatal lung disease 5