Neutrophilic asthma is a severe subtype of asthma that doesn’t respond well to typical asthma treatments. Neutrophils, a class of white blood cells, cause this type of asthma.

Asthma is a chronic disease of the lungs characterized by airway inflammation. While the term “asthma” broadly refers to inflammation and symptoms caused by airway constriction, such as wheezing and shortness of breath, there are several subtypes.

One such subtype of severe asthma is neutrophilic asthma. High levels of a type of white blood cell called neutrophils that accumulate in the lungs cause this type of asthma. These may then cause problems with airway obstruction.

While you might have signs of severe asthma, only a doctor can determine if you have the neutrophilic subtype. Here’s everything you need to know about neutrophilic asthma.

Experts categorize asthma in several ways. There are various subtypes based on cause or severity. One way of categorizing asthma is based on what causes inflammation.

Common inflammatory types of asthma include:

  • Allergic: Inhaling certain allergens can trigger allergic asthma.
  • Eosinophilic: This type of severe asthma is characterized by excess white blood cells called eosinophils.
  • Neutrophilic: White blood cells called neutrophils cause this type of asthma.
  • Mixed: This refers to the presence of both eosinophilic and neutrophilic asthma.
  • Paucigranulocytic: This subtype also consists of eosinophils and neutrophils but is less severe compared to the types listed above.

What is the role of neutrophils in asthma?

Neutrophils are a class of white blood cells. They’re an important part of your immune system. Not having enough neutrophils may increase your risk of infections.

However, with neutrophilic asthma, your lungs have too many of these white blood cells. They’re also present in airway mucus. These neutrophils worsen airway obstruction and can make typical asthma treatments ineffective.

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In general, any of the following may trigger severe asthma:

However, the triggers of neutrophilic asthma are different. Possible causes and risk factors include:

  • overuse of inhaled corticosteroids, which may increase neutrophil levels in your lungs
  • problems with the smooth muscles in your airways
  • chronic infections
  • smoking
  • obesity

There isn’t a single test to diagnose neutrophilic asthma. Instead, a doctor may diagnose you with this type of severe asthma if you need either:

  • continuous oral steroids for more than half the year
  • high dose inhaled corticosteroids on a regular basis

Aside from one of the above, you may also experience at least two of the following:

  • at least one visit to urgent care for asthma symptoms in the past year
  • a history or at least one near-fatal asthma event
  • consistent need for long-term controller medications, such as leukotriene receptor antagonists or long-acting beta-agonists
  • asthma symptoms that worsen after decreasing oral or inhaled corticosteroid dosage by 25%
  • persistent airway obstruction despite treatment
  • the need for short-acting beta-2-agonists (such as a rescue inhaler) on almost a daily basis despite taking long-term controller medications

A doctor may also diagnose neutrophilic asthma based on the following:

  • a neutrophil count of 5 million per milliliter in a mucus (sputum) sample
  • onset as young as age 12, but usually after 20 years old
  • symptoms that are worse at night
  • signs of airway remodeling on imaging tests
  • frequent hospital visits for asthma attacks
  • symptoms that don’t respond to strong treatments, such as steroids or biologics

Neutrophilic asthma doesn’t respond to typical severe asthma treatments, such as oral steroids or inhaled corticosteroids.

While researchers are still investigating effective treatments, one 2020 review states that neutrophilic asthma requires methods that help prevent or decrease airway remodeling.

This may involve one or a combination of the following options:

  • Long-acting PDE 4 inhibitors: These help to control an enzyme called phosphodiesterase (PDE), which certain inflammatory cells like neutrophils may express. Long-acting PDE 4 inhibitors may help decrease inflammation and subsequent airway changes caused by neutrophilic asthma.
  • Bronchial thermoplasty (BT): This outpatient procedure smooths airway muscles using radiofrequency waves. Doctors only recommend BT for adults who don’t have other underlying medical conditions.
  • Macrolide antibiotics: When used on a short-term basis, these types of antibiotics may decrease neutrophil levels in the lungs.

A doctor may recommend the following lifestyle changes to help manage neutrophilic asthma:

While severe asthma is rarely fatal, neutrophilic asthma subtypes are more difficult to control because of the lack of effective treatments currently available. As such, neutrophilic asthma is associated with:

  • more frequent visits to urgent cares and hospitals
  • medication side effects due to high doses or long-term use
  • reduced quality of life
  • increased risk of acute, fatal asthma attacks

As researchers continue to explore new treatment options, the outlook for people with neutrophilic asthma may improve.

When discussing neutrophilic asthma with a doctor, below are a few of the most common questions you might consider.

How common is neutrophilic asthma?

While exact numbers are unknown, experts think neutrophilic asthma is the most common type of adult-onset severe asthma. Most people with this subtype develop it after age 20.

What is the difference between eosinophilic and neutrophilic asthma?

Both eosinophilic and neutrophilic asthma are types of severe, inflammatory asthma. While excess neutrophils in the lungs cause neutrophilic asthma, excess eosinophils cause eosinophilic asthma.

Unlike neutrophilic asthma, eosinophilic asthma may respond to biologics.

What is the most severe type of asthma?

Having severe asthma means that your condition doesn’t respond to treatments as it should, or that your asthma requires long-term treatment of medium-to-high dose corticosteroids.

While neutrophilic asthma is a serious condition that often leads to hospitalization, the most severe type of asthma is an acute condition called status asthmaticus. This is a medical emergency that causes respiratory failure.

It’s also important to know that uncontrolled severe asthma can lead to status asthmaticus.

Neutrophilic asthma is a type of severe, inflammatory asthma caused by excess neutrophils in the lungs. It’s a complicated lung disease that can cause airway obstruction and doesn’t respond well to typical asthma treatments.

While the overall outlook for neutrophilic asthma is complicated, you may consider discussing emerging treatments with a doctor. Certain lifestyle changes may also help these treatment methods.