Severe Asthma: Understanding Eosinophilic Inflammation and New Treatments

For many, asthma management involves regular inhaler use and allergen avoidance. But, a significant group of patients experience persistent symptoms despite consistent medication and high doses, frequently requiring emergency room visits and hospitalizations. These individuals may have what doctors define as “severe asthma.” Understanding the underlying causes, particularly the role of eosinophilic inflammation, is crucial for effective treatment.

What is Severe Asthma?

Dr. Zheng Shilong, director of the Department of Chest Medicine at Yadong Memorial Hospital, clarifies that severe asthma isn’t defined by a single, particularly bad attack, but by the consistent difficulty in controlling the condition throughout the overall treatment process. This often stems from persistent inflammation within the body, with hypereosinophilia being a key indicator.

Severe Asthma vs. Typical Asthma

While typical asthma attacks are often triggered by external allergens like dust mites, pollen, and pet dander, severe asthma involves more complex underlying inflammatory mechanisms. Some patients don’t exhibit typical allergies but experience abnormal immune system reactions. A significant factor in these reactions is the overactivation and proliferation of eosinophilic white blood cells.

Eosinophilic white blood cells normally combat infections and mediate immune responses. However, when overactivated, they release toxic proteins into the lungs, causing persistent respiratory inflammation and heightened airway sensitivity, leading to frequent attacks.

Types of Severe Asthma

Severe asthma is categorized into four distinct types based on inflammation pathways and clinical presentation:

• Allergic Asthma: Often seen in younger patients with identifiable allergens and a high allergy index.
• Eosinophilic Asthma: Typically affects older patients without detectable allergens, often accompanied by nasal polyps or sinusitis. This type generally exhibits higher overall severity.
• Non-Allergic, Non-Eosinophilic Asthma: Frequently linked to repeated infections or viral infections, leaving airways chronically sensitive.
• Airway Remodeling Asthma: Characterized by structural changes in the airways, potentially diminishing the impact of allergy or inflammation indicators, and making treatment more challenging.

The allergic and eosinophilic types have the most well-defined treatment strategies. Identifying the specific type is essential for effective management, as avoiding allergens and standard medication may not be sufficient for all patients.

The Role of Eosinophilic White Blood Cells

Elevated eosinophilic white blood cell counts can be detected through blood tests. Normal levels for healthy adults are typically low (< 100 cells/µL). Values significantly above this threshold warrant further investigation. A count of 300 cells/µL or higher strongly suggests eosinophilic asthma.

If the inflammatory response of eosinophilic leukocytes intensifies, it can extend beyond the respiratory tract, potentially causing vascular inflammation, neuropathy, and skin lesions. In rare, severe cases, it can evolve into eosinophilic granulomatosis with polyangiitis (EGPA), a serious immune disease. Early identification and appropriate treatment are therefore vital.

New Treatment Options: Biologic Therapy

For severe asthma with eosinophilic inflammation, the treatment goal remains reducing attack frequency, minimizing oral steroid use, and improving quality of life and lung function. Biologic therapies have emerged as a precise treatment option by regulating key inflammatory pathways.

Dr. Zheng Shilong explains that these therapies target and block specific inflammatory mediators driving eosinophilic white blood cell activation and proliferation, inhibiting the excessive inflammatory response at its source and stabilizing the condition.

When to Seek Medical Attention

Dr. Zheng Shilong emphasizes that many patients initially mistake asthma symptoms for a common cold. However, a cold typically resolves quickly. A persistent cough lasting longer than two weeks, especially when accompanied by chest tightness, wheezing, or shortness of breath, warrants a prompt evaluation by a respiratory specialist to determine if asthma is present and to identify the specific type for targeted treatment.