BACKGROUND The diagnostic work-up and treatment of pulmonary hypertension can be complex. Pulmonary arterial hypertension (PAH), pulmonary hypertension second to lung or heart diseases and thromboembolic pulmonary hypertension, and other rare causes of pulmonary hypertension such as congenital heart diseases must be considered in the differential diagnostic work-up. CASE REPORT We report on a patient who has been treated for PAH over many years. At the age of 65, progressive symptoms required a complete re-evaluation. Here, a complex shunt vitium with a partial anomalous pulmonary venous return (PAPVR) and a sinus venosus defect (SVD) was diagnosed. CONCLUSIONS PAPVR is a rare congenital heart disease that is often associated with an SVD. It is usually diagnosed during childhood but may also be detected in adult patients who develop pulmonary hypertension and dyspnea as primary symptoms. The initial predominant left-to-right shunting associated with this disease may be undetected for years, with a slow development of right heart failure with right heart volume overload and pulmonary hypertension. Early detection is important, with a subsequent surgical intervention.