Sarcoidosis. This is an example of upper zone fibrosis caused by sarcoidosis. Note the increased interstitial markings in both upper zones. The fibrotic changes have pulled both of the hila superiorly (arrows). The commonly used mnemonic for the differential diagnosis for predominantly upper zone fibrosis is CHARTS, which is for Coal workers’ pneumoconiosis, Histiocytosis X, Ankylosing Spondylitis, Radiation, TB and Sarcoidosis/Silicosis. However, in reality we see very little of the ‘C’, ‘H’, ‘A’ or Silicosis these days. In SVUH we see a lot of cystic fibrosis, some historic cases of TB, and some sarcoidosis. Nowadays, radiation fibrosis tends to be a unilateral process, most commonly seen in patients who have had radiotherapy for breast cancer on that side. So, by all means remember the components of the CHARTS mnemonic for exam purposes, but bear in mind that in practice a CXR with upper zone fibrosis is most likely to represent a patient with CF, old TB, previous breast cancer or occasionally sarcoidosis.