Diffuse alveolar hemorrhage is a syndrome of recurrent or persistent bleeding into the lungs, caused most often by an autoimmune disorder.
Common symptoms are difficulty breathing and coughing, often coughing up blood.
People usually have chest imaging, blood tests, and sometimes examination of the breathing passages with a flexible viewing tube (bronchoscopy).
An important function of the immune system is fighting off infections. To do this, the immune system recognizes microorganisms as foreign to the person and produces proteins (antibodies) that bind to the microorganisms so they can be removed from the body. In autoimmune disorders, the body mistakenly reacts against a person's own tissues as if they were foreign. In autoimmune disorders that involve the lungs, the immune system attacks and damages lung tissue. Autoimmune disorders that affect the lungs can also affect other organs, like the kidneys.
Diffuse alveolar hemorrhage is a syndrome, not a particular disorder. A syndrome is a group of symptoms and other abnormalities that occur together but may be caused by several different disorders. Diffuse alveolar hemorrhage involves damage to the small blood vessels that supply the lungs, causing blood to accumulate in the tiny air sacs (alveoli) of the lungs. Such blood vessel damage can result from several disorders.
Causes of Diffuse Alveolar Hemorrhage
Many disorders can cause diffuse alveolar hemorrhage.
The most common causes are
Autoimmune disorders (for example, vasculitis and Goodpasture syndrome)
Other disorders that can cause diffuse alveolar hemorrhage include
Defective blood clotting caused by disorders or anticoagulant drugs
Heart disorders (for example, mitral stenosis)
Idiopathic pulmonary hemosiderosis (a rare disorder, possibly due to autoimmune injury, that causes only diffuse alveolar hemorrhage and typically affects children younger than 10 years)
Isolated pauci-immune pulmonary capillaritis (an immune disorder that affects people between ages 18 and 35 and damages the tiny blood vessels of the lungs, causing blood to leak into the lungs but no other problems)
Lung infections (for example, hantavirus infection)
Toxins (for example, isocyanates, crack cocaine, trimellitic anhydride, certain pesticides, and vaping)
Transplantation of organs or bone marrow
Symptoms of Diffuse Alveolar Hemorrhage
Diffuse alveolar hemorrhage syndrome can cause
Cough
Difficulty breathing
Fever
At least two thirds of people with diffuse alveolar hemorrhage cough up blood. When the disorder is severe, breathing may be extremely difficult. People may gasp and have bluish or pale and grayish discoloration of the skin (cyanosis). Some people die.
People may also have other symptoms typical of the disorder that caused the diffuse alveolar hemorrhage.
People who have repeated episodes of bleeding into the lungs can develop anemia (low blood count, often causing fatigue) and lung scarring that causes pulmonary fibrosis.
Diagnosis of Diffuse Alveolar Hemorrhage
Computed tomography scan of chest
Sometimes insertion of a flexible viewing tube into the lungs (bronchoscopy) with fluid wash out (bronchoalveolar lavage)
Doctors can often diagnose diffuse alveolar hemorrhage by a person's symptoms and chest imaging findings. If the diagnosis is not clear based on symptoms and chest imaging findings (for example, if the person has not coughed up blood), doctors may need to insert a flexible viewing tube into the lungs (bronchoscopy) and wash out the lungs with fluid (bronchoalveolar lavage) to check for small amounts of blood.
The level of red cells in the blood is measured to test for anemia.
After diffuse alveolar hemorrhage has been diagnosed, the cause must be determined. A variety of blood tests may be done, depending on what disorders seem to be likely causes. Urinalysis is done to tell whether the person has kidney damage, characteristic of the pulmonary-renal syndrome. Sometimes, when a cause remains unclear after these tests or the progression of disease is rapid, biopsy of the lungs or kidneys may be needed.
Treatment of Diffuse Alveolar Hemorrhage
Treat specific cause of disorder
Supportive measures
The disorder causing diffuse alveolar hemorrhage is treated.
Problems that people with diffuse alveolar hemorrhage also have, such as difficulty breathing and clotting disorders, are also treated. For example, people may be given oxygen or may need to be on a mechanical ventilator for a period of time.
Blood transfusions, plasma exchange, or other measures may also be needed.
