Lung diseases range from extremely common conditions like asthma, which affects millions of people worldwide, to rarer disorders like pulmonary hypertension. Some are caused by infections, others by genetics, and many by long-term exposure to irritants like cigarette smoke. Here are 10 lung diseases, what causes them, and how they affect the body.
1. Asthma
Asthma is a chronic condition where the airways overreact to triggers like pollen, cold air, exercise, or respiratory infections. When triggered, the smooth muscle surrounding the airways tightens, the airway lining swells, and excess mucus narrows the breathing passages. This combination causes wheezing, chest tightness, coughing, and shortness of breath. The underlying problem, called airway hyperresponsiveness, involves both direct stimulation of airway smooth muscle and indirect stimulation from immune cells like mast cells that release inflammatory chemicals.
Most people with asthma manage it well with inhaled medications that reduce inflammation and open the airways. Symptoms can range from mild and occasional to severe and daily, and the condition often starts in childhood, though adults can develop it too.
2. Chronic Obstructive Pulmonary Disease (COPD)
COPD is an umbrella term covering two related conditions: chronic bronchitis and emphysema. In chronic bronchitis, the airways stay inflamed and produce excess mucus, leading to a persistent cough. In emphysema, the tiny air sacs in the lungs are progressively destroyed, reducing the surface area available for oxygen exchange. Most people with COPD have elements of both.
Cigarette smoking causes the vast majority of COPD cases, though long-term exposure to air pollution, chemical fumes, or dust can also be responsible. The damage is irreversible, but quitting smoking slows the decline significantly. COPD develops gradually over years, and many people don’t notice symptoms until their lung function has already dropped substantially. Breathlessness during everyday activities like climbing stairs is often the first sign.
3. Lung Cancer
Lung cancer is the leading cause of cancer death worldwide. It comes in two main forms: non-small cell lung cancer (NSCLC), which accounts for roughly 80 to 85% of cases, and small cell lung cancer (SCLC), a faster-growing type strongly linked to smoking.
Survival depends heavily on how early the cancer is found. For NSCLC caught while still localized to the lung, the five-year survival rate is 67%. Once it has spread to distant parts of the body, that drops to 12%. Small cell lung cancer is more aggressive across the board: even localized SCLC has a five-year survival rate of just 34%, falling to 4% for distant-stage disease. According to the American Cancer Society, the overall five-year survival rate for all stages of NSCLC combined is 32%, compared to 9% for SCLC.
Smoking is by far the biggest risk factor, but about 10 to 20% of lung cancer cases occur in people who have never smoked. Radon exposure, secondhand smoke, and occupational chemicals also contribute.
4. Pneumonia
Pneumonia is an infection that inflames the air sacs in one or both lungs, filling them with fluid or pus. It can be caused by bacteria, viruses, or fungi. Symptoms typically include cough with phlegm, fever, chills, and difficulty breathing. For most otherwise healthy adults, pneumonia clears with treatment in one to three weeks. For older adults, young children, and people with weakened immune systems, it can become life-threatening.
Severity varies widely. Doctors assess factors like confusion, breathing rate, blood pressure, and age to determine whether someone can recover at home or needs hospital care. Viral pneumonia, including cases caused by influenza and COVID-19, doesn’t respond to antibiotics and is managed with supportive care. Bacterial pneumonia is treated with antibiotics, and most people start to feel better within a few days of starting them.
5. Pulmonary Fibrosis
Pulmonary fibrosis occurs when lung tissue becomes scarred and stiff. As scar tissue builds up in the air sacs, it becomes harder for oxygen to pass into the bloodstream. The most common form, idiopathic pulmonary fibrosis (IPF), has no identifiable cause. Other cases are linked to environmental exposures, autoimmune diseases, or certain medications.
The hallmark symptom is progressive breathlessness, first during exercise and eventually during simple daily activities. A dry, persistent cough is also common. You may have seen the statistic that average survival after an IPF diagnosis is three to five years. The Pulmonary Fibrosis Foundation notes this is an outdated figure. With earlier diagnosis and newer treatments that slow scarring, many people now live significantly longer. Two approved medications can slow the rate of lung function decline, though neither reverses existing scarring.
6. Pulmonary Embolism
A pulmonary embolism (PE) is a blood clot that travels to the lungs, usually from a deep vein in the leg. It blocks blood flow to part of the lung, which can damage lung tissue and drop oxygen levels throughout the body. Large clots can be fatal within hours.
Symptoms come on suddenly: sharp chest pain that worsens with deep breathing, unexplained shortness of breath, rapid heart rate, and sometimes coughing up blood. Risk factors include prolonged immobility (long flights, bed rest after surgery), recent surgery, cancer, pregnancy, and a personal or family history of blood clots. Treatment centers on blood-thinning medications that prevent the clot from growing while the body gradually dissolves it. In severe cases, more aggressive interventions are needed to remove or break up the clot directly.
7. Tuberculosis
Tuberculosis (TB) is a bacterial infection that primarily attacks the lungs. It spreads through the air when an infected person coughs or sneezes. Most people exposed to the bacteria develop a latent infection, meaning the bacteria are present but dormant, causing no symptoms and no contagiousness. About 5 to 10% of people with latent TB will eventually develop active disease if untreated.
Active TB causes a persistent cough lasting three weeks or more, chest pain, weight loss, night sweats, and sometimes coughing up blood. Standard treatment requires multiple antibiotics taken for six to nine months. A growing concern is drug-resistant TB. According to the World Health Organization, an estimated 390,000 people developed multidrug-resistant TB in 2024. While the proportion of new TB cases with drug resistance has dropped from 4.7% in 2015 to 3.2% in 2024, treatment for resistant strains is longer, more expensive, and harder on the body.
8. Cystic Fibrosis
Cystic fibrosis (CF) is a genetic disease that causes the body to produce abnormally thick, sticky mucus. In the lungs, this mucus clogs the airways and traps bacteria, leading to repeated infections, inflammation, and progressive lung damage. CF also affects the digestive system, making it difficult to absorb nutrients from food.
The outlook for people with CF has improved dramatically. A class of medications introduced in recent years targets the underlying protein defect rather than just managing symptoms. Based on 2024 data, the Cystic Fibrosis Foundation projects that babies born between 2020 and 2024 have a predicted median survival age of 65 years. That’s a remarkable shift from just a few decades ago, when most people with CF did not survive past their teens or twenties. Daily treatment still involves airway clearance techniques, inhaled medications to thin mucus, and antibiotics to fight lung infections.
9. Pulmonary Hypertension
Pulmonary hypertension is high blood pressure in the arteries that carry blood from the heart to the lungs. It’s diagnosed when the mean pressure in the pulmonary artery exceeds 20 mm Hg, measured by a catheter threaded into the right side of the heart. Normal pulmonary artery pressure is much lower than regular blood pressure, so even modest increases strain the heart.
There are five broad categories based on the underlying cause: pulmonary arterial hypertension (a disease of the artery walls themselves), left heart disease, lung diseases or low oxygen levels, blood clot obstructions in the pulmonary arteries, and a final group covering multifactorial or unclear causes like sickle cell disease. Symptoms include shortness of breath during activity, fatigue, dizziness, and swelling in the ankles or legs. Because the right side of the heart must pump harder against the increased pressure, pulmonary hypertension can eventually lead to right-sided heart failure if untreated.
10. Obstructive Sleep Apnea
Obstructive sleep apnea (OSA) might not seem like a lung disease in the traditional sense, but it directly affects airflow to the lungs. During sleep, the muscles in the throat relax and the airway repeatedly collapses, cutting off breathing for seconds to over a minute at a time. These episodes lower blood oxygen levels and fragment sleep.
Severity is measured by the apnea-hypopnea index (AHI), which counts how many times per hour breathing stops or becomes dangerously shallow. An AHI of 5 to 14 is mild, 15 to 30 is moderate, and above 30 is severe. The cardiovascular consequences are significant. A scientific statement from the American Heart Association links OSA to high blood pressure, atrial fibrillation, heart failure, coronary artery disease, stroke, and increased cardiovascular death. A meta-analysis of over 24,000 people found that severe OSA was associated with increased risk of dying from both cardiovascular causes and all causes combined.
The most common treatment is a CPAP machine, which delivers gentle air pressure through a mask to keep the airway open during sleep. Weight loss, positional therapy, and oral appliances that reposition the jaw are other options depending on severity.