Pediatric Thymus Rebound

  • Etiology: thymus shrinks due to stress (pneumonia, steroid therapy, chemotherapy, radiation therapy, surgery, burns), returns to normal or increased size when patient recovers over several months, is normal microscopically
  • Imaging: thymus disappears, then reappears but stops growing when it reaches its normal size, has homogenous appearance
  • DDX: recurrent tumor in a patient with an anterior mediastinal tumor

Radiology Cases of Thymus Rebound

CXR of thymic rebound
CXR AP from one month ago (left) shows evidence of a right lower lobe infiltrate and right pleural effusion due to bacterial pneumonia. The superior mediastinum is narrow. CXR AP taken today (right) shows resolution of the pneumonia and interval reappearance of the thymus.