Causes of AERD (Samter's Triad)
Why Do I Have This Disease?
The cause of Aspirin Exacerbated Respiratory Disease remains unknown. It does not appear to be a genetic or inherited disorder. Studies have found that only a small percentage of patients report a family history of NSAID sensitivity, which does not suggest a strong genetic component of the disease. It has been theorized that AERD may develop following exposure to a viral infection or environmental toxin, but the exact mechanism by which this may happen remains unclear. AERD is not considered an autoimmune disorder, but has instead been referred to as a "chronic immune dysregulation."
While the cause of AERD remains unknown, researchers have made many important findings about how the disease causes inflammation. Patients often have high levels of eosinophils (a type of white blood cell) in their blood and sinuses, which lead to chronic airway inflammation. It has also been found that AERD patients have an impaired cyclooxygenase enzyme (COX) pathway. Aspirin and NSAIDs block the COX-1 enzyme, which results in the reactions we experience when we ingest them. Even in the absence of exposure to NSAIDs, AERD patients have an increased production of leukotrienes and prostaglandins, inflammatory substances that produce allergy-like effects. Ingesting aspirin or NSAIDs drives production of these substances even higher, resulting in an acute reaction.
AERD Isn't Caused by Allergies
Our reactions to aspirin and other NSAIDs are not true "allergies" and are sometimes referred to as "pseudo-allergies" or hypersensitivity reactions. Allergies are triggered by immunoglobulin E (IgE), but the reactions in AERD are due to other mechanisms.
Some AERD patients did have allergies or asthma prior to developing AERD, but not all of us. Studies have shown that about 50-60% of patients have positive skin prick tests to environmental allergens. Many patients have no environmental allergies at all. For those who were perfectly healthy before developing AERD, the disease can feel like having "a cold that never went away."
The only environmental factor that has been linked to the development of AERD (Samter's Triad) is exposure to cigarette smoke. A 2012 study found that exposure to secondhand smoke in childhood increased the risk of developing AERD as an adult. Those who were exposed to secondhand smoke in childhood and also smoked in adulthood had an even greater chance of developing the disease. Despite this, the majority of people who develop AERD have never smoked. Exposure to cigarette smoke is not the cause of AERD, just one risk factor that has been identified.
Researchers are working hard to understand the causes of AERD. Do your part by completing Brigham & Women's Online AERD Survey.
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