Anatomy & Physiology: Current Research
Open Access

Pulmonary Hemorrhage

Diffuse alveolar hemorrhage results from widespread damage to the pulmonary small vessels, leading to blood collecting within the alveoli. If enough alveoli are affected, gas exchange is disrupted. The specific pathophysiology and manifestations vary depending on cause. For example, isolated pauci-immune pulmonary capillaritis is a small-vessel vasculitis limited to the lungs; its only manifestation is alveolar hemorrhage affecting people aged 18 to 35 years.

Symptoms and signs of milder diffuse alveolar hemorrhage are dyspnea, cough, and fever; however, many patients present with acute respiratory failure, sometimes leading to death. Hemoptysis is common but may be absent in up to one third of patients. Most patients have anemia and ongoing bleeding, leading to a reduced hematocrit.