A second entity seen in patients after modified Fontan procedure is "plastic bronchitis" (PB). This is a highly morbid clinical picture of persistent production of high mucoprotein-containing airway secretions that causes severe airway obstruction leading to increased work of breathing, V/Q mismatch and progressive respiratory failure leading to death. The etiology of plastic bronchitis is not understood at all and beyond supportive, palliative measures such as lung lavage, there is no current treatment for plastic bronchitis.