Rare Classroom: Eosinophilic Asthma

Welcome to the Rare Classroom, a new series from Patient Worthy. Rare Classroom is designed for the curious reader who wants to get informed on some of the rarest, most mysterious diseases and conditions. There are thousands of rare diseases out there, but only a very small number of them have viable treatments and regularly make the news. This series is an opportunity to learn the basics about some of the diseases that almost no one hears much about or that we otherwise haven’t been able to report on very often.

Eyes front and ears open. Class is now in session.

The rare disease that we will be learning about today is:

Eosinophilic Asthma

What is Eosinophilic Asthma?

  • A type of asthma with a prevalence of eosinophils in the airways
  • Eosinophilic inflammation is considered to be the main feature of allergic asthmatic
  • Eosinophilic inflammation is considered to be the way in which allergic asthma develops
  • An eosinophil is a proinflammatory white blood cell that has coarse granules in its cytoplasm
  • Interleukin-5 (IL-5) is the main promoter of eosinophil growth, activation and survival and provides an essential signal for the movement of eosinophils from the bone marrow into the lung
  • When a foreign substance enters the body, lymphocytes and neutrophils release substances that attract eosinophils and then release toxic substances to kill the invader
  • The numbers of eosinophils in blood often rise when an allergic reaction occurs
  • Eosinophilic functions include: movement to inflamed areas, trapping substances, killing cells, anti-parasitic and bactericidal activity, participating in immediate allergic reactions, and modulating inflammatory responses
  • Rare form of asthma including around 5% of cases

How Do You Get It?

  • It is not known why some individuals develop allergic responses but there are several hypotheses:
    • Some genetic and environmental factors interact, most often early in life
      • Some of the factors include:
        • An inherited tendency to develop allergies, called atopy 
        • Parents who have asthma
        • Certain respiratory infections during childhood
        • Contact with some airborne allergens or exposure to some viral infections in infancy or in early childhood when the immune system is developing
  • The “Hygiene Hypothesis”
    • The western lifestyle has resulted in improved sanitation resulting in less infections in early childhood. Young children’s immune systems develop during very early childhood, and it may increase their risk for asthma and atopy especially for children who have close family members with asthma and atopy
  • Not all patients with eosinophilic asthma have known allergies

What Are The Symptoms?

  • Symptoms of eosinophilic asthma are not currently differentiated from those of other asthma phenotypes. Symptoms include:
    • Shortness of breath
    • Wheezing
    • Breathlessness
    • Chest tightness
    • Coughing
  • The prevalence of symptoms did vary by phenotype according to one study.  The study found:
    • Coughing was associated with eosinophilic asthma, younger age (<10 years), female gender, and shorter disease duration, with positive family history of asthma.
    • Wheezing was associated with eosinophilic asthma and mixed asthma.
  • Eosinophilic airway inflammation appears to be much more closely related to the risk of severe asthma exacerbations

How Is It Treated?

  • Avoiding exposure to known allergens should always be part of treatment
  • Traditionally asthma treatments have been individualized using symptoms and measurements of pulmonary function (specifically spirometry/peak flow)
  • Treatment today has begun to be tailored based on inflammatory markers – e.g. sputum eosinophil count
  • Inhaled corticosteroids (ICS) are a major preventive treatment to control asthma symptoms – particularly those with eosinophilic inflammation. E.g. Pulmicort, Flovent, Qvar, Aerobid, Asmanex
  • Some common treatments for asthma may not work as well in eosinophilic asthma
  • Other treatments used in allergic asthma include:
    • Short–acting bronchodilators (rescue inhalers)
      • Include albuterol, Maxair, Proventil and Xopenex
    • Long-acting bronchodilators
      • salmeterol (Serevent, Advair) and formoterol (Foradil)
    • Anti-Leukotriene drugs
      • Accolate (zafirlukast), Singulair (available as the generic drug montelukast), and Zyflo (zileuton)
  • Oral Corticosteroids
    • Prednisone
  • Antibody Treatment
    • Xolair (omalizumab)
  • Combination treatment – Combines an ICS with a long-acting bronchodilator
    • Symbicort, Advair, Dulera, Anoro Ellipta
  • Immunotherapy

Where Can I Learn More???

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