Severe hypoxemia with orthodeoxia due to right to left shunt in idiopathicbronchiolitis obliterans with organizing pneumonia (BOOP)

We report a case of BOOP with severe hypoxemia and orthodeoxia. Chest X-ray showed bilateral infiltrative pneumonia and computed tomography scan revea led consolidations on lower lobes. Diagnosis of right-to-left shunt was mad e on the increase of alveolar-arterial oxygen difference under FIO2 100%, a ccented in standing position. Contrast-enhanced echocardiography and techne tium-99 macroaggregated albumin body scanning did not show anatomical right -to-left shunt and permitted the diagnosis of intrapulmonary shunt at the c apillary level because of intraalveolar organisation. Treatment with cortic osteroids and cyclophosphamide led to clinical, and radiological improvemen t with correction of the hypoxemia and the shunt.