It was Rendu who originally recognized the connection of epistaxis to cutaneous telangiectasia in 1896. Osler added three cases in 1901, and Weber described the familial nature of the cases and the lack of a coagulation abnormality. It is not clear how Osler's name became first in the eponym even before Hanes had named the syndrome "hereditary hemorrhagic telangiectasia (HHT)" in 1909. Most pulmonary arteriovenous malformations (PAVMs) have pulmonary arterial supply and pulmonary venous drainage with no intervening capillary beds. While multiple PAVMs are most typical of HHT, solitary examples certainly occur. Most PAVMs are found in the lower lobes, a location responsible for the characteristic symptom of platypnea (dyspnea in the upright position).
   
There is a controversy regarding whether all PAVMs are associated with HHT. Estimates of frequency of this association vary from 36% to 100%. The percentage of HHT patients who have PAVMs is less controversial, ranging from 15 to 50%. PAVMs may also be associated with cirrhosis, and tuberculosis (Rasmussen aneurysm).

Most patients with PAVMs present as asymptomatic young adults when a mass is detected on chest films. Symptoms, if present, can be non-specific, since hemoptysis only occurs in 10% to 15% of patients. Epistaxis is usually seen only in PAVM patients with HHT and is present in 32-85% of patients. The epistaxis may be mild to very severe, with up to 45 episodes per month. Many patients report daily epistaxis. Headache is also common in patients with HHT. Cutaneous telangiectasia occurs in up to 2/3 of patients with PAVMs and are characterized as small, red, vascular blemishes, most frequently on the face, that increase in size and number with age.

In cases where CT is not diagnostic of PAVMs, a perfusion lung scan may be used to detect a right-to-left shunt. Cardiac ultrasound may also be useful when performed with the contrast material indocyanine green. The appearance of this contrast is delayed in the left side of the heart. Pulmonary angiography is 100% sensitive for vessels of 2 mm and larger.

Complications of PAVMs include neurological abnormalities, especially cerebral abscess and other examples of "paradoxical" emboli, hypoxemia, as well as pulmonary symptoms, especially hemoptysis. Neurological problems in patients with HHT also include cerebral AVMs and spinal AVMs.

The treatment of PAVMs, originally limited to surgical resection, is now generally embolization. Coils of various sizes have produced excellent results with no mortality and with few complications. The feeding vessel must be 2-3 mm in diameter or larger and all feeding vessels must be embolized for success. Screening of HHT patients for PAVMs is very useful in improving prognosis and avoiding complications, especially cerebral abscess or stroke. Because the disease may be inherited, first degree relatives of patients with PAVMs should also be screened in order to avoid a clinical presentation precipitated by neurological complications. Spiral CT of the chest and clinical evaluation may be used for screening.