During the first couple of decades I had asthma, I was under the impression that asthma was just one disease that was the same experience, symptoms, and pathology for everyone. I knew that people had different triggers, but I never thought that there were different types of inflammation or patterns involved. Though, as I learned more about asthma, I came to understand that there are many different classifications. This article is going to dive into one of those specific branches: paucigranulocytic asthma.
Symptoms of asthma
The symptoms of asthma are similar across the different classifications of asthma.
It was not until treatment success varied between patients that research dove into understanding why some asthma was less responsive to medication. The result was the discovery of different asthma phenotypes.
The phenotype: paucigranulocytic
A ‘phenotype' is the physical or observable expression of a genetic system or ‘genotype'. There have been four main phenotypes identified to describe asthma: eosinophilic asthma, neutrophilic asthma, mixed granulocytic asthma, and paucigranulocytic asthma.1 For the purpose of readability, we are going to refer to paucigranulocytic asthma as ‘PGA’.
Three of the asthma phenotypes are defined by inflammation caused by different granules entering the airways. The expression of the PGA, however, is different. It is best understood by breaking down the word; pauci-, is a prefix meaning few and -granulocytic means to contain granules; so paucigranulocytic means to contain few granules. This refers to the number of inflammatory agents found in the sputum or blood, or lack thereof.1
PGA is also referred to as non-inflammatory asthma and is expressed as structural changes within the airways, rather than inflammation. This has been observed in ways such as airway smooth muscle tissue hypertrophy, commonly called airway remodeling. Research within animal models suggest that this might be due to a loss of homeostatic processes within the airways. This shift in physiological equilibrium is believed to be a possible cause of airway hyperresponsiveness in the PGA phenotype.1
Treatment of paucigranulocytic asthma
The lack of consistency between phenotypes can cause issues in the management of PGA. It is an anomaly compared to eosinophilic, neutrophilic, or mixed granulocytic asthma inflammation patterns, which are treated with similar medication.1
Many asthmatics report using corticosteroids as a treatment during attacks. However, research has shown that PGA shows little to no response to corticosteroid treatments. As a result, PGA has been deemed a “steroid-insensitive” phenotype. Further research is being directed towards alternative treatment options for those with PGA.1
Future research into paucigranulocytic asthma
As a phenotype that is more common among asthmatics that are considered well-controlled, there is less urgency to develop treatments for PGA as compared to other asthma phenotypes. After doing research for this article, it is clear that there has been little research done on PGA. Regardless, there is a great interest among researchers to understand more about the phenotype.
According to current researchers, "Further understanding of PGA with a focus on the characterization, prevalence, clinical significance, and pathobiology derived from animal studies will likely provide precision therapies that will improve PGA clinical outcomes."1 Hopefully, the future research of this PGA will bring better understanding and treatment for those that are afflicted with this unusual phenotype.
There is always a need for more research, although paucigranulocytic asthma has been a vastly understudied phenotype due to its typical mild severity. However, it is a chronic condition that influences people's lives and there has been expressed intention to better understand and develop more effective treatments.
What has your experience with Singulair been like?