Pulmonary arteriovenous malformations (PAVM) are abnormal direct communications between the pulmonary arteries and veins without the usual capillary bed. While pulmonary symptoms may include dyspnea, hypoxemia, and hemoptysis, these malformations are typically asymptomatic and are most commonly found incidentally on chest imaging. If symptoms occur, they often manifest in the fourth through sixth decades of life, although patients with hereditary hemorrhagic telangiectasia (HHT) may present earlier. Most patients have multiple PAVMs, although number, size, and distribution vary.

Most PAVMs are congenital and occur in patients with HHT, also known as Osler-Weber-Rendu syndrome. They can also occur in acquired conditions such as cirrhosis (most common), penetrating chest trauma, mitral stenosis, schistosomiasis, actinomycosis, Fanconi syndrome, and thyroid carcinoma. Some are idiopathic. The cause of PAVM is unknown.