Intensive Care Medicine (ICM) Practice Exam

What is the characteristic presentation of atypical pneumonia on a chest X-ray?

1. Atypical pneumonia

2. Community-acquired pneumonia

3. Pleural effusion

4. Pneumothorax

The correct answer is: Atypical pneumonia

Atypical pneumonia is commonly associated with certain characteristic radiological features on a chest X-ray. It is primarily caused by organisms such as Mycoplasma pneumoniae or Chlamydia pneumoniae. On imaging, atypical pneumonia typically presents as patchy infiltrates that may be bilateral and often do not follow the lobar distribution seen in typical pneumonia caused by Streptococcus pneumoniae. This unique presentation can lead to the appearance of interstitial patterns rather than the localized consolidation found in lobar pneumonia. In contrast, community-acquired pneumonia usually manifests with more pronounced lobar infiltrates, while conditions like pleural effusion and pneumothorax would show different signs, such as blunting of the costophrenic angles for effusion or visceral and parietal pleura separation on imaging for pneumothorax. Thus, the distinctive pattern of patchy or interstitial opacities on a chest X-ray is what specifically characterizes atypical pneumonia, making it the correct response in this context.