Eosinophilic bronchitis is a condition characterized by persistent coughing due to inflammation in the airways. This inflammation involves an increase in eosinophils, a specific type of white blood cell, within the bronchial lining. Unlike asthma, this condition does not lead to airway narrowing or difficulty breathing.
Recognizing the Signs
The primary symptom of eosinophilic bronchitis is a chronic cough, lasting for more than eight weeks in adults and four weeks in children. This cough is persistent and may worsen at night or with physical activity. While the cough can be dry, some individuals might produce clear or white mucus. Other common asthma symptoms like wheezing or shortness of breath are generally not present or are very mild with this condition. The cough in eosinophilic bronchitis is associated with an increased cough reflex, where even minor irritations can trigger a coughing fit.
Eosinophilic Bronchitis Versus Asthma
Eosinophilic bronchitis and asthma both involve airway inflammation with increased eosinophils. A key distinction lies in “bronchial hyperresponsiveness” or airway narrowing. In asthma, the airways become overly sensitive and constrict in response to triggers, leading to symptoms like wheezing and shortness of breath.
Eosinophilic bronchitis does not involve this airway hyperresponsiveness or variable airflow obstruction. The inflammatory process in eosinophilic bronchitis primarily affects the superficial airways, while in asthma, mast cells, another type of white blood cell, infiltrate the smooth muscle of the airways, contributing to their constriction. Consequently, the treatment approaches for these two conditions, while sometimes overlapping, are tailored to address these distinct physiological responses.
What Causes It
The exact cause of eosinophilic bronchitis is not fully understood, but it involves an immune response where eosinophils accumulate in the airways, leading to inflammation. This inflammation is often triggered by environmental factors. Common triggers include allergens like pollen, dust mites, and pet dander.
Irritants also play a role in triggering this condition, including exposure to smoke, chemical fumes, and occupational toxins like dust, formaldehyde, resin hardeners, and welding fumes. In some instances, certain infections or even gastroesophageal reflux (GERD) have been linked to the development of eosinophilic airway inflammation. The immune system overreacts to these triggers, causing the release of substances like histamine and prostaglandin D2, which contribute to the airway inflammation and the resulting chronic cough.
Diagnosis and Management
Diagnosing eosinophilic bronchitis typically involves a thorough medical history and physical examination, followed by specific tests to confirm the presence of eosinophilic inflammation and rule out other causes of chronic cough. A key diagnostic test is sputum induction, a non-invasive procedure where a saline solution is inhaled to help produce mucus. The collected sputum is then analyzed for an elevated eosinophil count, typically exceeding 3% of white blood cells, which is a hallmark of the condition. Bronchial challenge tests, such as a methacholine challenge, are also performed to confirm the absence of airway hyperresponsiveness, further distinguishing it from asthma.
Management of eosinophilic bronchitis primarily involves reducing airway inflammation. The first-line treatment is often inhaled corticosteroids, such as budesonide, which are effective in reducing both cough symptoms and eosinophil levels in the sputum. These medications are typically taken via an inhaler, sometimes with a nebulizer. While some individuals may see improvement within a few weeks, others might require longer-term treatment, potentially for several months, to prevent recurrence. Avoiding identified environmental triggers, such as dust or chemical fumes, also forms a part of the overall management strategy.