Impaired pulmonary perfusion associated with thymus hyperplasia in an infant candidate for Fontan operation.

An enlarged thymus adversely affected pulmonary artery development and perfusion in a 4-month-old boy with asplenia syndrome and a single ventricular circulation with aorto-pulmonary shunt. Steroid administration for 4 weeks successfully reduced thymus volume, concomitant with improvement of pulmonary vasculature and perfusion. Given the importance of pulmonary physiology in the Fontan circulation, the effects of thymic hyperplasia on pulmonary circulation should be taken into consideration in the overall management of candidates for Fontan surgery.