 About 70% to 90% of the patients with PAVMs have hereditary hemorrhagic telangiectasia (HHT) [2]. HHT is an autosomal dominant disorder associated with mutations in genes coding for endoglin and activin receptor-like kinase 1ALK1. The former leads to a phenotypical presentation with cerebral and PAVMs described as HHT type 1 [3]. The later presents with pulmonary hypertension and hepatic AVMs and is described as HHT type 2 [4]. Of patients with HHT, 1% to 2% have a SMAD4 mutation and a clinical phenotype associated with juvenile polyposis syndrome [5]. The clinical diagnosis of HHT is based on the Curacao criteria [6]. The prevalence of PAVM occurs in 1 in 5,000 individuals in the general population but can vary depending on the geographical distribution of HHT. In areas where HHT is more prevalent, PAVM prevalence can reach between 26 and 56 per 100,000 individuals. In general, there is a 1.5 to 2 times higher incidence of PAVMs in women compared to men but a male-predominance is noted in newborns [7]. Other causes of PAVMs are rare and include trauma, chest surgery, schistosomiasis, actinomycosis, mitral valve stenosis, Fanconi syndrome, cirrhosis with hepatopulmonary syndrome, and metastatic cancer [7]. Clinical manifestations of PAVMs depend on the size, number, type (complex versus simple), and flow through the malformations. Most patients are asymptomatic (25%-58%). Hypoxemia (27%-71%) at rest or exercise, especially orthodeoxia (worsening hypoxemia when upright) and platypnea (worsening dyspnea when upright), are classical presentations as 65% to 83% of PAVMs are in the lower lobes of the lungs [8]. Transient ischemic attacks and cerebral strokes (3.2%-55%), systemic infections, and abscesses including cerebral abscesses (0%-25%) and rarely massive hemoptysis and hemothorax (0%-2%) are other manifestations [1].
Pulmonary Arteriovenous Malformation PAVM .  About 70% to 90% of the patients with PAVMs have hereditary hemorrhagic telangiectasia (HHT) [2]. HHT is an autosomal dominant disorder associated with mutations in genes coding for endoglin and activin receptor-like kinase 1ALK1. The former leads to a phenotypical presentation with cerebral and PAVMs described as HHT type 1 [3]. The later presents with pulmonary hypertension and hepatic AVMs and is described as HHT type 2 [4]. Of patients with HHT, 1% to 2% have a SMAD4 mutation and a clinical phenotype associated with juvenile polyposis syndrome [5]. The clinical diagnosis of HHT is based on the Curacao criteria [6]. The prevalence of PAVM occurs in 1 in 5,000 individuals in the general population but can vary depending on the geographical distribution of HHT. In areas where HHT is more prevalent, PAVM prevalence can reach between 26 and 56 per 100,000 individuals. In general, there is a 1.5 to 2 times higher incidence of PAVMs in women compared to men but a male-predominance is noted in newborns [7]. Other causes of PAVMs are rare and include trauma, chest surgery, schistosomiasis, actinomycosis, mitral valve stenosis, Fanconi syndrome, cirrhosis with hepatopulmonary syndrome, and metastatic cancer [7]. Clinical manifestations of PAVMs depend on the size, number, type (complex versus simple), and flow through the malformations. Most patients are asymptomatic (25%-58%). Hypoxemia (27%-71%) at rest or exercise, especially orthodeoxia (worsening hypoxemia when upright) and platypnea (worsening dyspnea when upright), are classical presentations as 65% to 83% of PAVMs are in the lower lobes of the lungs [8]. Transient ischemic attacks and cerebral strokes (3.2%-55%), systemic infections, and abscesses including cerebral abscesses (0%-25%) and rarely massive hemoptysis and hemothorax (0%-2%) are other manifestations [1].