Partial anomalous pulmonary venous return (PAPVR) is a rare anatomical variant with estimated prevalence of between 0.1 - 0.5%. Left upper lobe PAPVR is the most common type, and is least associated with other abnormalities. PAPVR causes an extra-cardiac left-to-right shunt, however this is often not clinically significant,  thus patients may present late, or the diagnosis may be picked up incidentally on imaging (as was the case with this patient).