What Causes Pulmonary Sarcoidosis? Here’s What We Know
Pulmonary sarcoidosis is an inflammatory disease that mainly affects the lungs but can also involve other organs like the skin, lymph nodes, eyes, nervous system or even the heart. Despite being known to medicine for over a century, the exact cause of sarcoidosis remains a puzzle. This can be frustrating for patients looking for clear answers, but research is ongoing and new insights are constantly emerging. In this article, we’ll walk you through what we currently know about the possible causes of pulmonary sarcoidosis and who may be at higher risk.
No Clear Cause – A Medical Puzzle
Sarcoidosis is classified as a disease of unknown origin (idiopathic). This means there’s no single confirmed trigger or factor that explains why it develops in certain people and not in others. What we do know is that it’s a disorder of the immune system that leads to the formation of granulomas – small clusters of inflammatory cells. These are most commonly found in the lungs and chest lymph nodes, but they can also appear in many other parts of the body.
What Are Granulomas and Why Do They Form?
Granulomas are a way the body walls off substances it considers harmful – such as infections or foreign particles. However, in sarcoidosis, these inflammatory clusters form without any identifiable threat. It’s as if the immune system is fighting something invisible, and in doing so, it starts to damage healthy tissues.
If these granulomas don’t go away or spread, they can lead to chronic inflammation, scarring (fibrosis), and impaired organ function – especially in the lungs.
The Immune System – The Main Suspect
Research has shown that specific immune cells, especially CD4+ T lymphocytes and activated macrophages accumulate in the affected tissues and drive the formation of granulomas. One of the leading theories is that sarcoidosis results from an overactive immune response of this kind. Simply put: the immune system overreacts to certain stimuli – such as dust, bacteria, or chemicals – and triggers an ongoing inflammatory process that doesn’t shut off properly. This suggests that while the immune system is central to the disease, it may be reacting to something that, in healthy individuals, wouldn’t cause a problem.
Environmental Triggers – What We Breathe Might Matter
There’s growing evidence that environmental exposures may play a role in triggering sarcoidosis, especially in people who are genetically predisposed. Some of these triggers may include:
- Organic and inorganic dusts – including mold, pollen, plant material, or dust in farming or industrial environments.
- Chemical substances – such as pesticides, solvents, and certain metals (e.g., beryllium, aluminum, titanium) found in construction, welding, or manufacturing.
- Air pollution – including smog, fumes, or fine particulate matter, which can irritate the lungs and contribute to chronic inflammation.
While many people are exposed to these factors daily, not everyone develops sarcoidosis – suggesting that environmental triggers are only one piece of the puzzle.
Could Infections Be a Trigger?
Another theory proposes that infections – especially bacterial or viral – might act as a spark for sarcoidosis. Researchers have investigated certain microbes, including Mycobacterium (similar to the bacteria that cause tuberculosis) and Propionibacterium, as potential culprits.
In this model, the infection doesn’t directly cause sarcoidosis, but it may set off an immune reaction that, in genetically predisposed individuals, spirals into chronic inflammation and granuloma formation.
Who’s at Higher Risk?
Although sarcoidosis can affect anyone, certain factors appear to increase the likelihood of developing it:
- Age: Most often diagnosed in people between 20 and 40 years old.
- Gender: In some populations, women are more commonly affected than men.
- Ethnicity: People of African, Scandinavian, or Irish descent may have a higher risk.
- Genetics: If a close family member has sarcoidosis, your risk is somewhat higher. Researchers have also identified certain genes associated with increased susceptibility.
These risk factors don’t guarantee that someone will develop sarcoidosis, but they can help doctors identify who may need closer monitoring.
Does Lifestyle Matter?
There’s no direct link between lifestyle habits and the development of sarcoidosis, but how we live can still have an indirect impact on our health and how the disease progresses.
- Smoking can worsen lung function and increase complications.
- Poor diet and lack of exercise can weaken the immune system and reduce overall resilience.
- Chronic stress may influence immune system balance and inflammatory responses.
While these factors don’t cause sarcoidosis, a healthy lifestyle can support better outcomes, help manage symptoms, and improve quality of life.
In Summary
Although the cause of pulmonary sarcoidosis remains unknown, current research points to an abnormal immune response influenced by genetic factors, environmental exposures, and possibly infections. What we do know is that the immune system plays a central role, and in some people, it reacts in ways that lead to persistent inflammation and granuloma formation in the lungs.
If you’re experiencing symptoms like a persistent cough, shortness of breath, unexplained fatigue, or swollen lymph nodes, it’s important to see a doctor. Early diagnosis can lead to better management and avoidance of affecting multiple organs.