Eli5: how does a double lung transplant not “cure” COPD?


I don’t understand how a person still has COPD if they receive new lungs, I can’t find an explanation for this

In: 2

While replacing both lungs through a lung transplant can greatly improve the quality of life for individuals with chronic obstructive pulmonary disease (COPD), it may not necessarily cure the condition entirely. COPD is a progressive lung disease primarily caused by long-term exposure to irritants such as smoking or environmental pollutants.

When a person undergoes a lung transplant, the damaged lungs are replaced with healthy ones. However, even with new lungs, the underlying causes of COPD, such as inflammation and airway damage, may still persist. These issues can continue to affect the respiratory system, leading to potential complications. Additionally, the immune system may still be affected, as COPD can have systemic effects beyond just the lungs.

Furthermore, COPD is often associated with other health conditions like heart disease or lung infections, which may not be resolved by a lung transplant alone. These comorbidities can contribute to the overall management and progression of the disease.

In the United States in 2023, the overwhelmingly most common cause of COPD is tobacco use. A small fraction is caused by genetic issues like Alpha-1 anti trypsin deficiency. I’m not talking about asthma, which is technically an obstructive lung disease which is chronic; I’m talking about the chronic bronchitis variety, which is more common in older adults.

Someone who actively smokes tobacco would not be offered a lung transplant. So the driver for COPD would be absent after the transplant. The new lungs don’t develop COPD. So in a sense, the patient is cured of COPD. However receiving a transplant organ is not a perfect fix. The person must take medications to suppress their immune system so as to prevent their body from rejecting the new lungs. In lung transplant recipients the doses of immunosuppressive are particularly high, since the lung receives a lot of blood (100% of the cardiac output) and is therefore exposed to a lot of immune cells. Some patients reject their lung grafts even in spite of the immunosuppressants. This lung rejection can manifest many ways, one of which is a problem called “bronchiolitis obliterans.” This chronic form of lung graft rejection is characterised by inflammation in the airways resulting in narrowing of the airway passages, which can produce symptoms very similar to COPD itself. However this is not COPD, as the causes and treatments are different.

Another issue with immunosuppressive after lung transplant is the infection risk. Lungs are exposed to air, which is full of all sorts of viruses/bacteria/fungi/yeast/spores and stuff that a healthy immune system normally obliterates without issue. But the immunosuppression required to mitigate the risk of lung rejection also attenuates the body’s ability to fight infection, so lung transplant recipients are very vulnerable to infection. This can also make people very sick and cause chronic problems in lung grafts. However this is not COPD either.

So TL;DR as long as the recipient quits smoking, lung transplantation does cure COPD. It just comes with a bunch of different problems that can also be really serious.