Cor triatriatum sinister: a rare underlying cause of pulmonary hemosiderosis.

Pulmonary hemosiderosis is a disorder with unknown cause and characterized by hemosiderin appreciation in alveolar interstitium from decomposed hemoglobin following alveolar capillary bleeding, which finally leads to pulmonary fibrosis. It can be divided into primary and secondary types in terms of its etiology. While primary types are related to autoimmunity, secondary types can be associated with cardiovascular and pulmonary causes such as mitral stenosis leading to pulmonary congestion. We report a case of cor triatriatum sinister in a child who presented with hemoptysis as a main clinical manifestation and had been previously diagnosed with idiopathic pulmonary hemosiderosis. Based on clinical signs and imaging examinations, we considered the hemoptysis was most likely due to cor triatriatum. The child underwent corrective surgery with uneventful recovery. The hemoptysis has not recurred any more after operation. Cardiovascular disease including cor triatriatum should be considered with regards to the etiology of pulmonary hemosiderosis.