Idiopathic Pulmonary Hemorrhage

Idiopathic pulmonary hemorrhage is a rare condition that affects the lower respiratory tract. It can be divided into two clinical entities depending on whether the pathophysiology and presentation are acute or chronic. Acute idiopathic pulmonary hemorrhage usually presents as diffuse alveolar hemorrhage (DAH), while the more insidious or chronic pulmonary hemorrhage often presents as idiopathic pulmonary hemosiderosis (IPH) following repeated alveolar bleeding. The terms idiopathic pulmonary hemorrhage, idiopathic pulmonary hemosiderosis, and diffuse alveolar hemorrhage are often used interchangeably. Historically, idiopathic pulmonary hemorrhage was first described by Virchow in 1864 as brown lung induration. Ceelen in 1931 gave a more detailed description of the condition after autopsies revealed large amounts of hemosiderin in 2 children, while Waldenstrom, in 1944, made the first antemortem diagnosis. Pulmonary hemorrhage is the extravasation of blood into the alveoli, that is, bleeding into the lower respiratory tract. It can be severe and life-threatening. In diffuse alveolar hemorrhage (DAH), the bleeding is usually of sudden onset, and is widespread and not limited to a section of the lungs. In idiopathic pulmonary hemosiderosis (IPH), repeated alveolar hemorrhage causes the accumulation of hemosiderin, a by-product of hemoglobin breakdown, in the alveoli. Alveolar macrophages take up these hemosiderin molecules, usually within 36 - 72 hours, and can remain in the lungs for up to 8 weeks. Acute idiopathic pulmonary hemorrhage in infants (AIPHI) is a rare, quite distinct clinical presentation of the condition that occurs in infants and is characterized by the sudden onset of pulmonary bleeding in a previously healthy infant in the absence of other known co-morbidities including prematurity.The clinical spectrum of IPH ranges from asymptomatic cases to life-threatening acute respiratory failure. AIPHI often presents acutely with severe respiratory distress. Due to its rarity and varied presentations, IPH often causes a diagnostic pitfall for many clinicians. Unfortunately, delayed diagnosis leads to delayed treatment and, ultimately, a poor outcome.