Heterotaxy syndrome is a rare clinical entity in adults, characterized by situs ambiguus, congenital heart defects, and splenic malformations. We report the case of an adult with heterotaxy syndrome (including situs ambiguus, bilateral superior vena cava, hypoplastic right-sided spleen and portosystemic shunts) presenting with dyspnea due to severe pulmonary hypertension. Vasodilatory therapy was initiated, leading to marked reduction of clinical symptoms. This case exhibits 2 particular and partially novel features: primary diagnosis of heterotaxy syndrome may be delayed until adulthood, and heterotaxy syndrome may be associated with pulmonary hypertension, possibly on the basis of longstanding portosystemic shunts.