Pulmonary hemorrhage is bleeding that occurs inside the lungs, specifically in the tiny air sacs (alveoli) where oxygen normally passes into your bloodstream. Instead of air filling these sacs, blood leaks in from damaged blood vessels, interfering with breathing and oxygen exchange. The condition ranges from mild, slow bleeding that builds up over time to sudden, life-threatening episodes. In-hospital mortality for the most serious form, called diffuse alveolar hemorrhage, runs around 25%.
How Bleeding Starts in the Lungs
Your lungs contain millions of alveoli, each surrounded by a network of extremely small blood vessels called capillaries. A thin membrane separates the air inside the alveoli from the blood flowing through those capillaries. When that membrane is damaged, whether by inflammation, immune system attack, or injury, blood seeps through into the air spaces.
Once blood enters the alveoli, it blocks the normal exchange of oxygen and carbon dioxide. White blood cells called macrophages rush in to clean up the blood, absorbing iron from the red blood cells in the process. These iron-loaded macrophages are a hallmark of the condition and one of the key ways doctors confirm a diagnosis. Over time, repeated episodes of bleeding leave iron deposits throughout the lung tissue, which can cause scarring and permanent damage.
Common Causes
Autoimmune diseases are the most frequent trigger. In these conditions, the immune system mistakenly attacks the blood vessels or membranes in the lungs. Anti-glomerular basement membrane disease (sometimes called Goodpasture syndrome) directly targets the thin membrane in both the lungs and kidneys. Vasculitis, a group of diseases that inflame blood vessels, can destroy the tiny capillaries surrounding the alveoli. Lupus is another well-known autoimmune cause.
But autoimmune disease isn’t the only path to pulmonary hemorrhage. Other causes include:
- Blood clotting problems, whether from a clotting disorder or from anticoagulant medications
- Heart conditions, particularly mitral valve stenosis, which raises pressure in the blood vessels of the lungs
- Infections, including hantavirus and other respiratory viruses
- Drugs and toxins, including crack cocaine, certain chemotherapy agents, some pesticides, and chemicals inhaled through vaping
- Organ or bone marrow transplantation, which can trigger bleeding as a complication
In rare cases, no underlying cause is ever identified. This is called idiopathic pulmonary hemosiderosis, and it primarily affects young children, with the average age at diagnosis around 4.5 years.
Symptoms to Recognize
The classic pattern involves three things happening together: coughing up blood (hemoptysis), low red blood cell counts from ongoing blood loss, and abnormal shadows on a chest X-ray or CT scan. Not everyone experiences all three at once. Some people never cough up visible blood, especially in early or mild cases. Instead, the bleeding stays contained deep in the lung tissue, causing symptoms that mimic pneumonia or other lung conditions.
Shortness of breath is often the most noticeable symptom, and it can come on gradually or hit suddenly depending on how fast the bleeding occurs. Fatigue and weakness from anemia are common, particularly when bleeding has been going on for weeks or months without being recognized. A persistent cough, fever, and chest discomfort round out the typical picture. In severe episodes, oxygen levels drop quickly enough to require emergency care.
How It’s Diagnosed
Chest imaging is usually the first step. On a CT scan, pulmonary hemorrhage typically shows up as hazy, ground-glass opacities, areas where the lungs look cloudy instead of clear. These tend to appear on both sides of the lungs in a relatively symmetrical pattern, concentrated around the central areas. The tricky part is that this pattern looks very similar to fluid buildup from heart failure. A history of autoimmune disease or coughing up blood helps point doctors in the right direction.
The most reliable diagnostic tool is a procedure called bronchoalveolar lavage. A thin, flexible tube is passed into the airways, and small amounts of sterile fluid are washed into a section of the lung, then suctioned back out for analysis. In pulmonary hemorrhage, this fluid comes back progressively bloodier with each sample. Under a microscope, the presence of iron-loaded macrophages confirms that bleeding has been occurring. The commonly used threshold is finding these iron-loaded cells making up at least 20% of all macrophages in the sample, though this finding alone isn’t definitive since other forms of lung injury can produce similar results.
Blood tests looking for specific antibodies help identify the underlying autoimmune cause, and kidney function tests are important because several of the diseases that cause lung bleeding also damage the kidneys simultaneously.
Treatment and Recovery
Immediate treatment focuses on two priorities: keeping oxygen levels stable and stopping the bleeding. People with severe episodes often need supplemental oxygen, and some require mechanical ventilation if their lungs can’t keep up. Blood transfusions replace what’s been lost when anemia becomes dangerous.
If a clotting problem is contributing to the bleeding, correcting it with clotting factors or reversing anticoagulant medications is a first step. Medications that help blood clot, delivered as a mist directly into the airways through a nebulizer, can slow active bleeding at the source. When the initial medication isn’t enough to control bleeding within the first 24 hours, stronger clotting agents may be added.
For autoimmune causes, which represent the largest group, the goal is to shut down the immune attack on the lung’s blood vessels. Corticosteroids are the cornerstone of treatment, often given at high doses initially and then tapered over weeks to months. Many patients need a second immunosuppressive medication added on top of steroids to keep the disease controlled long term. In pediatric idiopathic pulmonary hemosiderosis, 76% of children in one study required long-term steroid therapy, and nearly half needed additional immunosuppressive drugs to prevent recurrent bleeding episodes.
Long-Term Outlook
Pulmonary hemorrhage is serious. A study of 97 patients published in the European Respiratory Journal found that about 1 in 4 patients died during their hospital stay. Among those who survived to discharge, another 16% died over a follow-up period averaging about three years. Notably, outcomes were similar whether the cause was autoimmune or non-autoimmune.
The long-term picture depends heavily on the underlying cause and how quickly treatment starts. People with autoimmune-driven bleeding who respond well to immunosuppressive therapy can go into remission, though relapses are common and require ongoing monitoring. Repeated episodes of bleeding cause cumulative scarring in the lungs, which gradually reduces lung function over time. For children with idiopathic pulmonary hemosiderosis, research suggests that sustained immunosuppressive treatment improves outcomes compared to short or no treatment, though many of these children deal with the condition for years.
Recovery from an acute episode typically involves weeks of gradual improvement as the blood in the alveoli is cleared by the body’s cleanup cells. Lingering shortness of breath and reduced exercise tolerance are normal during this period. Regular follow-up imaging and lung function testing help track whether the lungs are healing or whether scarring is developing.