Background: The “hepatic factor,” a molecule or group of molecules present in the hepatic
venous blood, essential for the prevention of the development of pulmonary arteriovenous malformations
(PAVMs) and right-to-left shunting has been a conceptual enigma in the understanding of
many related conditions.
Methods: Patients with various forms of liver diseases including acute hepatic failure, and others
with normal hepatic function like hereditary hemorrhagic telangiectasia (HHT), inflammatory and
parasitic disorders, cardiogenic hepatopulmonary syndrome (cHPS) and skin disorders like Dyskeratosis
congenita are all known to cause PAVMs. Over a period of the last two decades our understanding
of the pathogenesis of PAVMs has changed, but the mechanisms are still not clearly understood.
The presence of PAVMs once considered a contraindication for liver transplantation is now a cure
for PAVMs in patients with HPS.
Results: In this article the molecular mechanisms and the underlying pathogenesis of PAVMs are
discussed and the role of microRNA (miRNA) in its pathogenesis is favorably argued. Identifying
and preventing or treating the underlying mechanisms will significantly influence the management of
a large group of patients who at present cannot be effectively treated with a very poor prognosis.
Progressive polycythemia, desaturation, stroke, and infection are serious complications of PAVMs.
Conclusion: The clinical data and current understanding leads to the possible role of miRNA, which
inhibits Vascular Endothelial Growth Factor (VEGF) synthesis as a pathogenic mechanism for the
development of PAVMs.