associated with Marfan syndrome, congenital heart disease (atrial septal defect)
shift of heart to left, straightening of left heart border, prominence of main pulmonary artery segment, loss of descending aortic interface, increased opacity in right cardiophrenic angle, loss of clarity of right heart border, steep inferior slope of anterior ribs, undue clarity of lower dorsal spine
pecus carinatum (pigeon chest) is the reverse deformity, may be congenital or acquired