Today is rare disease day. Does Severe Asthma qualify as a rare disease. This is a relatively new sub-group of asthma, and some champion for it to be a disease entity of it's own, with it's own treatment guidelines.
Asthma affects about 10 percent of the world's population, and severe asthma affects about 10 percent of asthmatics. So that should make it pretty rare.
Typical asthma presents with chronically inflamed airways that are oversensitive to environmental triggers. Asthma attacks are completely reversible with time or treatment. It responds well to corticosteroid therapy, and therefore asthma attacks can be prevented and controlled. Between attacks breathing is normal.
Severe asthma, on the other hand, presents with airway remodelling, mainly the thickening of the smooth muscles lining airways. This makes the walls of airways abnormally thick, creating chronically narrowed airways. It responds poorly to corticosteroid therapy, and therefore asthma attacks are more frequent and severe. Between attacks there is always some degree of dyspnea.
While steroids don't seem to work for sufferers of severe asthma, some evidence seems to point to Gallopamil as a future treatment option. This is a calcium channel blocker generally used to treat cardiac arrhythmias. Studies show that it may may lesson the mass of airway smooth muscles, making their airway walls less thick. This makes it so the airways are not so obstructed, thus making breathing easier.