Extrinsic vs Intrinsic Asthma
In 1918, asthma was considered a symptom of allergies, and the treatment was allergy shots. Dr. Francis Rackemann, however, observed most of his asthma patients did not have allergies, and did not benefit from allergy shots. To assure all asthmatics were properly diagnosed and treated, he proposed dividing asthma into various subgroups under two headings: extrinsic and intrinsic asthma.1 So, what are these, and what does it mean for you?
First, let’s set the stage
Very little was known about asthma--and nothing about allergies--until the early 1900's. Asthma was thought to be a nervous condition that caused a narrowing of airways and shortness of breath when exposed to exciting factors, like stress. They knew about hay fever and that it was caused by pollen, but they did not know the mechanisms for what caused the sniffling and sneezing.1,2
Then, in 1901, epinephrine was discovered, and it was discovered to rapidly cure asthma episodes. This spearheaded a hunt to learn how it worked and what causes asthma. That same year, the Prince of Morocco summoned two scientists to study the Portuguese man-of-war to see if they could find a way to protect swimmers from it’s painful sting. Their efforts ultimately lead to the discovery of allergies.2
By 1910, Dr. Samuel Meltzer suggested that asthma was a symptoms of allergies, and that treating asthma was as simple as injecting the right protein into the asthmatic. This theory was well accepted by the medical community until Dr. Rackemann published his ideas about extrinsic and intrinsic asthma in 1918 and again in 1947. By 1947, he had begun to wonder if asthma was a disease rather than a symptom. As more evidence was learned about our disease, his assumption would prove to be true.1,2
Rackemann described extrinsic asthma as caused by inhaling or ingesting foreign substances (later known as allergens) from “without the body." Some causes were in the air, such as horse hair, plant pollens, and feather dust, and some were in the foods ingested, such as eggs, berries, fish, and cereals. Depending on the likely cause, asthma was then broken down into subgroups, such as horse asthma, pollen asthma, or food asthma.2,3
Extrinsic asthma was considered seasonal, as symptoms come and go with the seasons. For instance, asthma associated with hay fever was most common in the spring, although went away when the hay season ended. It was also considered environmental. For instance, asthma caused by dust would improve upon removal of the asthmatic from the dusty environment. If a feather pillow was the culprit, the remedy was removal of the pillow from the patient’s environment. Food asthma was resolved by not eating the offending food.2,3
Exposure to any of these substances may cause an asthmatic immune system to develop proteins that were later discovered to be IgE antibodies. The asthmatic is then said to be sensitized to that particular substance, and subsequent exposures cause the allergy and asthma responses. The treatment for this was allergy shots, or immunotherapy, which gradually introduced that allergen so the asthmatic could be “desensitized” to it over time.4
Subtypes of extrinsic asthma
The subtype of asthma could be diagnosed by an accurate history, although most likely it involved allergy skin testing. It was also most commonly diagnosed in childhood, and usually by the age of 12, at least according to Rackemann.2
Extrinsic asthma today
Today, extrinsic asthma is generally referred to as the asthma subgroup allergic asthma, and this is regardless of the allergens involved. It can be diagnosed by a positive allergy test to dust mites feces, mold spores, animal dander, cockroach urine, and certain foods. As Rackemann noted, allergic asthma is most often diagnosed in childhood, although it can be diagnosed at any age.2 More recent studies show a new diagnosis of allergies is also quite common in the elderly population.
Rackemann described this as asthma caused by substances from “within the body.” These patients usually have a negative allergy skin test, and therefore do not have allergies and do not benefit from allergy shots or allergy medications.3
Rackemann believed a common cause of intrinsic asthma was colds, and treating the asthma was as simple as avoiding getting a cold. One suggested remedy here was vaccination.3 Other than colds, he suggested sinus infections, chronic sinusitis, teeth infections, gum infections, and throat infections, as probable causes of asthma. The likely treatment would be the treatment of the infection, or avoiding it altogether.2,3,5
Nasal polyps were a probable cause, and treatment was removal of polyps. Gastrointestinal irritation was also a probable cause, and treatment was finding what was causing the trouble and resolving that. He also described nervous asthma as a subgroup of intrinsic asthma, and the treatment was treating the person as a whole.2,3
He described intrinsic asthma as nonseasonal, more likely to become chronic, and said it is usually diagnosed in adulthood. The treatment of intrinsic asthma involved treatment of the internal cause. For example, treating the infection, removal of polyps, resolving croup or learning what’s causing gastrointestinal irritation and resolving that.2Subtypes of intrinsic asthmaSubgroups of asthma that generally fall under the heading intrinsic would include any subgroup except for allergies. These include exercise induced asthma, gastrointestinal reflux (GERD) asthma, premenstrual asthma, aspirin sensitive asthma, cough variant asthma, obese asthma, rhinitis induced asthma, vitamin D deficiency asthma, occupational asthma, psychiatric induced asthma, and many others.3,4Intrinsic asthma todayWhether this is a good definition or not, intrinsic asthma is now generally considered to be asthma caused by anything other than allergens, and this includes external factors such as chemicals in cigarette and wood smoke, high humidity, cold air, strong smells, viruses and bacteria. It also includes internal factors such as gastrointestinal reflux, strong emotions (crying and laughing), anxiety, and stress.5Many books state that intrinsic asthma is most often diagnosed in adulthood, although we now understand that this is not always the case. For instance, I had a friend back in 1985 who was diagnosed with GERD asthma when he was 15, although it wasn’t called that back then. I know many asthmatics, including myself, who were diagnosed with exercise-induced asthma as children. Asthma caused by premature birth would also be considered intrinsic.5However, I think we can safely say that most cases of intrinsic asthma are diagnosed in adulthood, and this is mainly because the older we get the more problems occur within our bodies. For example, GERD asthma is most likely diagnosed in adulthood. Occupational asthma and premenopausal asthma are obviously diagnosed in adulthood.5Asthma subgroups were created with good intentionsBack in the day, the terms intrinsic and extrinsic were important because they encouraged physicians to search for specific causes in order to find the best treatment options for individual asthmatics. Nearly a hundred years later, efforts are still ongoing to define asthma subgroups, and this shows that Rackemann was right on track.1,2Today, genetic research is being utilized to further break asthma into subgroups, and this should continue the trend away from treating all asthmatics the same and towards developing individualized asthma treatment programs that help each asthmatic obtain ideal asthma control. Do you have extrinsic or intrinsic asthma? Share in the comments below!
Does cold weather impact your asthma?