Asthma has traditionally been considered a disorder of the lungs.  This makes sense since a tell-tale sign of this disease is difficulty with breathing. Yet the evolution of the term might soon include more than just the lungs.  

In a sense, as more evidence has come to fruition over the 5,000 year history of asthma, the definition has evolved.  The word asthma was first used by the ancient Greeks, as "asthmae," which means short, gasping breaths. 

Basically, even into the early 20th century, all that caused shortness of breath was referred to as asthma, including bronchitis, emphysema, pneumonia and heart failure. 

Yet eventually those diseases earned their own categories, and the asthma definition evolved into what we know it as today. 

By 1959 asthma was defined as a disease where the air passages (bronchioles) of your lungs become narrow (bronchospasm) and this is reversible either spontaneously or with medicine. 

By 1962 asthma was defined as a disease whereby the bronchioles become hyperresponsive and narrow as a result of exposure to various stimuli (asthma triggers). 

By 1987 the key component was defined as airway obstruction caused when the lungs are exposed to asthma triggers.  This obstruction consists of airway narrowing caused by bronchial muscle spasms (bronchospasm), increased mucus production, and swelling of the cells surrounding the lungs (inflammation).

By 2000, the term evolved to include two key components. 

• Chronic inflammation: Swelling of the airways that is always there.  The severity of asthma is determined by the degree of swelling.  Likewise, this swelling can be controlled with asthma controller medicines.
• Acute Bronchospasm:  Exposure to asthma triggers can make this inflammation worse, thus causing airway narrowing. This can be reversed with time or with medicine.  Likewise, in many cases, this can be prevented with medicines, control of inflammation, and avoidance of asthma triggers.

That's where we stand today, although with studies ongoing, and scientists now studying the newly found asthma genes, it's possible this definition will continue its evolution.

Another thing that might further evolve the definition of asthma is the fact this disease has been linked to various other systems of the body, kind of like the way cystic fibrosis effects not just the lungs but the kidneys too. 

Thus, in reality, asthma may be more than just a lung disease.  The following is a list of systems currently believed to be linked with asthma:

1.  Lungs :  Well, we already knew this.  It causes difficulty breathing.

2.  Autoimmune system: For an unknown reason (however there are theories), the immune systems of people with asthma recognize harmless substances such as dust mites, molds, animal dander, and cockroach urine as harmful, and attacks these as though they were harmful substances like viruses and bacteria.  This results in the so called asthma and allergy attacks.  It has been proven that 75 percent of asthmatics have allergies.  So you'll see many asthmatics on allergy meds such as antihistamines, decongestants, and leukotriene blockers.