Asthma Subgroups: Mixed Granulocytic Asthma

About 5-10% of asthmatics have severe asthma.¹ This is asthma that is difficult to control despite compliance with all the best treatment options. One asthma subgroup that falls under this severe asthma heading is “mixed granulocytic asthma.” So, what is it? How is it characterized? Here’s what to know.

What does "granulocytic" mean?

Granulocytes are an integral part of your immune system. They are white blood cells that contain little granules. These granules may include cytokines. When you have an infection, granulocytes travel to the infected area and release their granules. Some travel to the infected area and cause inflammation. Others travel through your bloodstream to call for reinforcements.²

Granulocytes also play a role in asthma. Two granulocytes that may contribute to asthma are eosinophils and neutrophils.

Eosinophils

It’s also a type of severe asthma.  I wrote about eosinophils in my article, “What are Eosinophils?” I described how they contribute to asthma in “What is Eosinophilic Asthma?” This type of asthma is now well defined and understood. It can be diagnosed with a blood eosinophil level of greater than 2-3%. It may also cause nasal polyps to develop.^3-6

Most people diagnosed with it can obtain good asthma control with a combination of front-line asthma medicines, such as inhaled corticosteroids. One granule known to be responsible is a cytokine called Interleukin 5 (IL5). So it may also respond well biologics that block the effects of IL5. Currently, there are five such biologics on the market.^3-6

Neutrophils

Neutrophilic asthma is also a type of severe asthma. Neutrophilic inflammation is a more aggressive type of inflammation. It is not as well understood as eosinophilic asthma. What is known is it tends to be less responsive to beta agonists and corticosteroids. It may also be combined with a diagnosis of GERD.^3-6

The best test for diagnosing it has yet to be determined. Unlike eosinophilic asthma, it cannot be diagnosed with a blood neutrophil level (at least not yet). So, diagnosing may entail a more invasive sputum or cell sample directly from airways. Neutrophil levels should be elevated, potentially as high as 40-76%. Researchers think it is caused by a cytokine called Interleukin 17 (1L17).^3-6

There are currently no biologics approved for neutrophilic asthma (although there are some in the pipeline). So, the best treatment options have yet to be determined.^3-6

What is mixed granulocytic asthma?

Mixed granulocytic asthma is a rare type of severe asthma. People with this subtype have both eosinophilic and neutrophilic airway inflammation. This is another subgroup of asthma that is not well understood. Like neutrophilic asthma, it tends to respond poorly to front-line asthma medicines. Unlike eosinophilic asthma, it tends to be less associated with nasal polyps. Unlike neutrophilic asthma, it tends to be less associated with GERD. It is usually only diagnosed in older adults.^3-6

Other characteristics include of mixed granulocytic asthma include:³

• It’s a form of severe asthma.
• Asthma attacks may appear frequently.
• These asthma attacks may be difficult to treat.
• People with it may respond poorly to corticosteroids (may be due to IL17)
• They may have airway remodeling or scarring.
• They may be more prone to bacterial lung infections.
• They may have a difficult time obtaining good asthma control.
• This is a rare form of asthma.

Some experts think it might be caused by a bacterial infection. This may explain how IL5 gets involved, as it responds to the bacteria. Another theory is it’s caused by exposure to indoor dust. Yet another is that it’s caused by exposure to cigarette smoke. It may also be a type of occupational asthma. And there are other theories attempting to explain it.³

What to make of this?

I purposefully inserted the links in this article. If you want further information you can click on them if you want. It’s so neat what researchers are learning about asthma. That they are aware of mixed granulocytic asthma offers hope for those who have it. They are working overtime to learn more about it, and strategies for treating it. As we learn more, we will share it with you.