Diffuse Alveolar Hemorrhage: A Medical Emergency with High Mortality

Diffuse alveolar hemorrhage (DAH) is a life - threatening pulmonary complication, originates from the pulmonary microvasculature, including the alveolar capillaries, arterioles, and venules. DAH is characterized by the effusion of blood into the alveoli caused by numerous diseases related to hemoptysis, hypoxemia due to alveolar collapse, anemia, diffuse lung infiltration, acute respiratory failure, and death. DAH is usually diffuse but may also be focal. DAH should be distinguished from another mechanism of pulmonary hemorrhage due to localized pulmonary abnormalities and bronchial circulation. Pulmonary hemorrhage can arise from the small, medium, and large pulmonary vessels are typically due to systemic vasculitis, which is one of the most common etiology of DAH. Vasculitis involving the microvasculature is known as pulmonary capillaritis.