Case Study Discussion

Now we need to consider the possible differentials. In terms of the CT scan, we have clear evidence of lower lobe predominant architectural distortion with honeycomb change and peripheral reticulation, all of which would indicate definite UIP. However, we also notice that there are clear areas of air trapping, which are noticeable on the TLC series and were confirmed on the residual volume series. The presence of multifocal areas of air trapping excludes the diagnosis of definite or even probable UIP and is a clear CT signal for hypersensitivity pneumonitis. So, in this case, the CT scan was very helpful in guiding us away from IPF and giving us a diagnosis of HP.