Bronchiectasis is not an autoimmune disease. It is a chronic lung condition defined by permanent widening of the airways, driven by a cycle of infection and inflammation rather than by the immune system attacking healthy tissue. However, the relationship between bronchiectasis and autoimmune disease is closer than many people realize: several autoimmune conditions significantly raise the risk of developing bronchiectasis, and in some patients, an autoimmune disease is the underlying cause.
What Bronchiectasis Actually Is
Bronchiectasis develops when the airways (bronchi) become permanently stretched and damaged. Roughly 500,000 people in the United States have the non-cystic fibrosis form, and it becomes far more common with age: prevalence jumps from about 7 per 100,000 in adults aged 18 to 34 to 812 per 100,000 in those 75 and older. Women are affected nearly twice as often as men.
The condition follows what researchers call a “vicious cycle.” It typically starts with some initial insult, whether a severe lung infection, an immune deficiency, or chronic inflammation from another disease. That insult impairs the lungs’ natural cleaning system, the layer of mucus and tiny hair-like structures that sweep debris and bacteria out of the airways. Once this system falters, bacteria settle in and multiply. The body sends waves of immune cells to fight the infection, but those immune cells release destructive enzymes that damage the airway walls. The damage makes it even harder to clear mucus, which breeds more infection, which triggers more inflammation. Over time, the elastic tissue and cartilage that give airways their shape break down, leaving them permanently dilated.
A key player in this destruction is a specific enzyme released by neutrophils, the most common type of white blood cell at the site. This enzyme degrades elastin, the protein responsible for the lungs’ flexibility, and triggers excess mucus production. It also activates other tissue-degrading enzymes and kills airway lining cells directly. The result is a protease-antiprotease imbalance: the destructive enzymes overwhelm the body’s natural defenses against them.
Why It Gets Confused With Autoimmune Disease
The confusion is understandable. Bronchiectasis involves chronic, damaging inflammation, and it frequently shows up alongside autoimmune conditions. But the distinction matters. In autoimmune disease, the immune system specifically targets the body’s own tissues as if they were foreign invaders. In bronchiectasis, the immune system is responding to real threats (bacteria colonizing the airways) but doing so in a way that causes collateral damage. The inflammation is excessive and self-perpetuating, but it is not autoimmune in origin.
That said, when an autoimmune disease is the trigger that starts the vicious cycle, the line can feel blurry. The underlying autoimmune process creates the conditions for bronchiectasis to develop, even though the airway damage itself follows the infection-inflammation pattern rather than direct autoimmune attack on lung tissue.
Autoimmune Diseases That Cause Bronchiectasis
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is one of the most common autoimmune conditions linked to bronchiectasis. A meta-analysis of 36 studies found that when RA patients were screened with high-resolution CT scans, about 22.6% had bronchiectasis. Many had no idea. Risk factors include older age, longer disease duration, and certain genetic markers. Patients who had lived with RA for an average of nearly nine years were significantly more likely to have bronchiectasis than those with shorter disease duration (about five years on average).
The connection likely involves both the systemic inflammation of RA and the immune dysfunction that comes with it. RA can cause chronic airway inflammation independently of infection, and the medications used to treat it can also suppress immune defenses enough to allow recurrent lung infections.
Sjögren’s Syndrome
Sjögren’s syndrome, an autoimmune disease best known for causing dry eyes and dry mouth, frequently affects the lungs. Airway disease is its most common pulmonary complication. The same immune cells that infiltrate and damage moisture-producing glands throughout the body also infiltrate the bronchial walls, even in patients with no respiratory symptoms and normal chest X-rays. CT studies have found bronchiectasis in anywhere from 7% to 54% of Sjögren’s patients.
The mechanism is two-pronged. The disease destroys the glands that keep airways moist, drying out the mucus layer that normally traps and removes bacteria. At the same time, immune cells (primarily a type of T lymphocyte) infiltrate the airway lining and cause direct inflammation. Specific autoantibodies produced in Sjögren’s syndrome may also contribute to bronchial damage. Together, these factors create ideal conditions for the infection-inflammation cycle to take hold.
Other Connective Tissue Diseases
Bronchiectasis can also develop in the context of other autoimmune and connective tissue diseases, including lupus and systemic sclerosis. These conditions put patients at risk for a range of pulmonary problems, from airway-centered disorders like bronchiectasis and bronchiolitis to deeper lung scarring (interstitial lung disease) and pulmonary hypertension. The pattern of lung involvement varies by disease and by individual, which is why CT imaging plays such an important role in sorting out what’s happening in the lungs.
Other Common Causes
Autoimmune disease is just one category of trigger. The full list of causes is long, and in many patients, no clear cause is ever identified.
- Past lung infections: A severe pneumonia, tuberculosis, or whooping cough earlier in life can leave enough airway damage to start the vicious cycle. Post-infectious bronchiectasis accounts for a substantial share of cases.
- Immune deficiencies: Primary immunodeficiencies, especially common variable immune deficiency (CVID), are a major cause. Between 27% and 79% of CVID patients develop bronchiectasis because their bodies cannot produce enough antibodies to fight off respiratory infections. In one French study, a third of patients seen for immune-deficiency-related lung problems had bronchiectasis.
- Cystic fibrosis and ciliary disorders: Genetic conditions that impair mucus clearance, whether through abnormally thick mucus or defective cilia, are well-established causes.
- Idiopathic: In roughly 15 to 20% of cases, no underlying cause is found despite thorough testing.
How Bronchiectasis Is Diagnosed
The gold standard is a high-resolution CT scan of the chest. Doctors look at the ratio between the width of an airway and the artery running alongside it. In healthy lungs, these are roughly the same diameter. When the airway is noticeably wider than its companion artery, that signals bronchiectasis. Additional signs include airway wall thickening and mucus plugging visible on the scan.
Once bronchiectasis is confirmed, the next step is figuring out why it developed. This typically involves blood tests for immune function (including antibody levels), screening for autoimmune markers, sputum cultures to identify which bacteria have colonized the airways, and sometimes genetic testing. Identifying an underlying autoimmune disease or immune deficiency changes the treatment approach considerably, since addressing the root cause can slow further lung damage.
How Severity Is Measured
Doctors use scoring systems to gauge how serious bronchiectasis is and predict its course. The most widely used is the FACED score, which considers five factors: lung function (measured by a breathing test), age, whether bacteria have chronically colonized the airways, how many lobes of the lung are affected, and the degree of breathlessness. Scores of 0 to 2 indicate mild disease, 3 to 4 moderate, and 5 to 7 severe. These scores help guide how aggressively the condition is managed and how closely patients need to be monitored over time.
For patients whose bronchiectasis is driven by an autoimmune condition, managing the autoimmune disease itself is a critical part of the picture. Controlling systemic inflammation can help slow the progression of airway damage, though the structural changes already present in the lungs are permanent. The goal shifts to preventing further deterioration, keeping infections under control, and maintaining the best possible lung function.